1
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Nagae T, Takeda M, Noji T, Saito K, Aoyama H, Miyanoiri Y, Ito Y, Kainosho M, Hirose Y, Ishikita H, Mishima M. Direct evidence for a deprotonated lysine serving as a H-bond "acceptor" in a photoreceptor protein. Proc Natl Acad Sci U S A 2024; 121:e2404472121. [PMID: 39190358 PMCID: PMC11388336 DOI: 10.1073/pnas.2404472121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Accepted: 07/11/2024] [Indexed: 08/28/2024] Open
Abstract
Deprotonation or suppression of the pKa of the amino group of a lysine sidechain is a widely recognized phenomenon whereby the sidechain amino group transiently can act as a nucleophile at the active site of enzymatic reactions. However, a deprotonated lysine and its molecular interactions have not been directly experimentally detected. Here, we demonstrate a deprotonated lysine stably serving as an "acceptor" in a H-bond between the photosensor protein RcaE and its chromophore. Signal splitting and trans-H-bond J coupling observed by NMR spectroscopy provide direct evidence that Lys261 is deprotonated and serves as a H-bond acceptor for the chromophore NH group. Quantum mechanical/molecular mechanical calculations also indicate that this H-bond exists stably. Interestingly, the sidechain amino group of the lysine can act as both donor and acceptor. The remarkable shift in the H-bond characteristics arises from a decrease in solvation, triggered by photoisomerization. Our results provide insights into the dual role of this lysine. This mechanism has broad implications for other biological reactions in which lysine plays a role.
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Affiliation(s)
- Takayuki Nagae
- Department of Molecular Biophysics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
| | - Mitsuhiro Takeda
- Department of Molecular Biophysics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
| | - Tomoyasu Noji
- Research Center for Advanced Science and Technology, The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 118-8656, Japan
| | - Keisuke Saito
- Research Center for Advanced Science and Technology, The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 118-8656, Japan
| | - Hiroshi Aoyama
- Department of Molecular Biophysics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
| | - Yohei Miyanoiri
- Research Center for State-of-the-Art Functional Protein Analysis, Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Yutaka Ito
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji 192-0397, Japan
| | - Masatsune Kainosho
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji 192-0397, Japan
| | - Yuu Hirose
- Department of Applied Chemistry and Life Science, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan
| | - Hiroshi Ishikita
- Research Center for Advanced Science and Technology, The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 118-8656, Japan
| | - Masaki Mishima
- Department of Molecular Biophysics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
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2
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Lanza L, Rabe von Pappenheim F, Bjarnesen D, Leogrande C, Paul A, Krug L, Tittmann K, Müller M. Identification and Characterization of Thiamine Diphosphate-Dependent Lyases with an Unusual CDG Motif. Angew Chem Int Ed Engl 2024; 63:e202404045. [PMID: 38874074 DOI: 10.1002/anie.202404045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 05/21/2024] [Accepted: 05/22/2024] [Indexed: 06/15/2024]
Abstract
The thiamine diphosphate (ThDP)-binding motif, characterized by the canonical GDG(X)24-27N sequence, is highly conserved among ThDP-dependent enzymes. We investigated a ThDP-dependent lyase (JanthE from Janthinobacterium sp. HH01) with an unusual cysteine (C458) replacing the first glycine of this motif. JanthE exhibits a high substrate promiscuity and accepts long aliphatic α-keto acids as donors. Sterically hindered aromatic aldehydes or non-activated ketones are acceptor substrates, giving access to a variety of secondary and tertiary alcohols as carboligation products. The crystal structure solved at a resolution of 1.9 Å reveals that C458 is not primarily involved in cofactor binding as previously thought for the canonical glycine. Instead, it coordinates methionine 406, thus ensuring the integrity of the active site and the enzyme activity. In addition, we have determined the long-sought genuine tetrahedral intermediates formed with pyruvate and 2-oxobutyrate in the pre-decarboxylation states and deciphered the atomic details for their stabilization in the active site. Collectively, we unravel an unexpected role for the first residue of the ThDP-binding motif and unlock a family of lyases that can perform valuable carboligation reactions.
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Affiliation(s)
- Lucrezia Lanza
- Institute of Pharmaceutical Sciences, Albert-Ludwigs-Universität Freiburg, Albertstrasse 25, 79104, Freiburg im Breisgau, Germany
| | - Fabian Rabe von Pappenheim
- Department of Molecular Enzymology, Georg-August Universität Göttingen, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Daniela Bjarnesen
- Institute of Pharmaceutical Sciences, Albert-Ludwigs-Universität Freiburg, Albertstrasse 25, 79104, Freiburg im Breisgau, Germany
| | - Camilla Leogrande
- Department of Molecular Enzymology, Georg-August Universität Göttingen, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Alexandra Paul
- Institute of Pharmaceutical Sciences, Albert-Ludwigs-Universität Freiburg, Albertstrasse 25, 79104, Freiburg im Breisgau, Germany
| | - Leonhard Krug
- Institute of Pharmaceutical Sciences, Albert-Ludwigs-Universität Freiburg, Albertstrasse 25, 79104, Freiburg im Breisgau, Germany
| | - Kai Tittmann
- Department of Molecular Enzymology, Georg-August Universität Göttingen, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Michael Müller
- Institute of Pharmaceutical Sciences, Albert-Ludwigs-Universität Freiburg, Albertstrasse 25, 79104, Freiburg im Breisgau, Germany
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3
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Noji T, Chiba Y, Saito K, Ishikita H. Energetics of the H-Bond Network in Exiguobacterium sibiricum Rhodopsin. Biochemistry 2024; 63:1505-1512. [PMID: 38745402 PMCID: PMC11155677 DOI: 10.1021/acs.biochem.4c00182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Revised: 05/08/2024] [Accepted: 05/08/2024] [Indexed: 05/16/2024]
Abstract
Exiguobacterium sibiricum rhodopsin (ESR) functions as a light-driven proton pump utilizing Lys96 for proton uptake and maintaining its activity over a wide pH range. Using a combination of methodologies including the linear Poisson-Boltzmann equation and a quantum mechanical/molecular mechanical approach with a polarizable continuum model, we explore the microscopic mechanisms underlying its pumping activity. Lys96, the primary proton uptake site, remains deprotonated owing to the loss of solvation in the ESR protein environment. Asp85, serving as a proton acceptor group for Lys96, does not form a low-barrier H-bond with His57. Instead, deprotonated Asp85 forms a salt-bridge with protonated His57, and the proton is predominantly located at the His57 moiety. Glu214, the only acidic residue at the end of the H-bond network exhibits a pKa value of ∼6, slightly elevated due to solvation loss. It seems likely that the H-bond network [Asp85···His57···H2O···Glu214] serves as a proton-conducting pathway toward the protein bulk surface.
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Affiliation(s)
- Tomoyasu Noji
- Department
of Applied Chemistry, The University of
Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research
Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Yoshihiro Chiba
- Department
of Applied Chemistry, The University of
Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Keisuke Saito
- Department
of Applied Chemistry, The University of
Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research
Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Hiroshi Ishikita
- Department
of Applied Chemistry, The University of
Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research
Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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4
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Uranga J, Mata RA. The Catalytic Mechanism of Acetoacetate Decarboxylase: A Detailed Study of Schiff Base Formation, Protonation States, and Their Impact on Catalysis. J Chem Inf Model 2023; 63:3118-3127. [PMID: 37127583 DOI: 10.1021/acs.jcim.3c00241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The enzyme acetoacetate decarboxylase (AAD) has a crucial function in the process of decarboxylating the substrate acetoacetate (AA). It has been extensively studied over the years, but its exact catalytic mechanism has remained partly unsolved due to the difficulty in assessing reaction intermediates. In this study, we combine molecular dynamics and electronic structure calculations to rediscover its catalytic mechanism. Our results show that the presence of the substrate, the acetoacetate, significantly influences the electrostatic potential of the active site. Furthermore, our simulations show that the decarboxylation reaction can take place by means of a direct proton transfer instead of via an enamine intermediate, which is thought to be strictly necessary. This work provides new insights into the role of the electrostatic interactions on the catalytic activity of AAD and for the first time connects it to the catalytic mechanism of other decarboxylases.
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Affiliation(s)
- Jon Uranga
- Institute of Physical Chemistry, Georg-August Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Ricardo A Mata
- Institute of Physical Chemistry, Georg-August Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
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5
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Zhang X, Wang Z, Li Z, Shaik S, Wang B. [4Fe–4S]-Mediated Proton-Coupled Electron Transfer Enables the Efficient Degradation of Chloroalkenes by Reductive Dehalogenases. ACS Catal 2023. [DOI: 10.1021/acscatal.2c06306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Xuan Zhang
- State Key Laboratory Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
| | - Zikuan Wang
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, Mülheim an der Ruhr 45470, Germany
| | - Zhen Li
- State Key Laboratory Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Binju Wang
- State Key Laboratory Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
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6
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Kozaeva E, Nieto-Domínguez M, Hernández AD, Nikel PI. Synthetic metabolism for in vitro acetone biosynthesis driven by ATP regeneration. RSC Chem Biol 2022; 3:1331-1341. [PMID: 36349222 PMCID: PMC9627730 DOI: 10.1039/d2cb00170e] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 09/15/2022] [Indexed: 05/14/2024] Open
Abstract
In vitro ketone production continues to be a challenge due to the biochemical features of the enzymes involved-even when some of them have been extensively characterized (e.g. thiolase from Clostridium acetobutylicum), the assembly of synthetic enzyme cascades still face significant limitations (including issues with protein aggregation and multimerization). Here, we designed and assembled a self-sustaining enzyme cascade with acetone yields close to the theoretical maximum using acetate as the only carbon input. The efficiency of this system was further boosted by coupling the enzymatic sequence to a two-step ATP-regeneration system that enables continuous, cost-effective acetone biosynthesis. Furthermore, simple methods were implemented for purifying the enzymes necessary for this synthetic metabolism, including a first-case example on the isolation of a heterotetrameric acetate:coenzyme A transferase by affinity chromatography.
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Affiliation(s)
- Ekaterina Kozaeva
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark 2800 Kongens Lyngby Denmark +93 51 19 18
| | - Manuel Nieto-Domínguez
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark 2800 Kongens Lyngby Denmark +93 51 19 18
| | - Abril D Hernández
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark 2800 Kongens Lyngby Denmark +93 51 19 18
| | - Pablo I Nikel
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark 2800 Kongens Lyngby Denmark +93 51 19 18
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7
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Petrovskaya LE, Lukashev EP, Siletsky SA, Imasheva ES, Wang JM, Mamedov MD, Kryukova EA, Dolgikh DA, Rubin AB, Kirpichnikov MP, Balashov SP, Lanyi JK. Proton transfer reactions in donor site mutants of ESR, a retinal protein from Exiguobacterium sibiricum. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2022; 234:112529. [PMID: 35878544 DOI: 10.1016/j.jphotobiol.2022.112529] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 07/04/2022] [Accepted: 07/14/2022] [Indexed: 06/15/2023]
Abstract
Light-driven proton transport by microbial retinal proteins such as archaeal bacteriorhodopsin involves carboxylic residues as internal proton donors to the catalytic center which is a retinal Schiff base (SB). The proton donor, Asp96 in bacteriorhodopsin, supplies a proton to the transiently deprotonated Schiff base during the photochemical cycle. Subsequent proton uptake resets the protonated state of the donor. This two step process became a distinctive signature of retinal based proton pumps. Similar steps are observed also in many natural variants of bacterial proteorhodopsins and xanthorhodopsins where glutamic acid residues serve as a proton donor. Recently, however, an exception to this rule was found. A retinal protein from Exiguobacterium sibiricum, ESR, contains a Lys residue in place of Asp or Glu, which facilitates proton transfer from the bulk to the SB. Lys96 can be functionally replaced with the more common donor residues, Asp or Glu. Proton transfer to the SB in the mutants containing these replacements (K96E and K96D/A47T) is much faster than in the proteins lacking the proton donor (K96A and similar mutants), and in the case of K96D/A47T, comparable with that in the wild type, indicating that carboxylic residues can replace Lys96 as proton donors in ESR. We show here that there are important differences in the functioning of these residues in ESR from the way Asp96 functions in bacteriorhodopsin. Reprotonation of the SB and proton uptake from the bulk occur almost simultaneously during the M to N transition (as in the wild type ESR at neutral pH), whereas in bacteriorhodopsin these two steps are well separated in time and occur during the M to N and N to O transitions, respectively.
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Affiliation(s)
- Lada E Petrovskaya
- Shemyakin & Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya, 16/10, Moscow 117997, Russia.
| | - Evgeniy P Lukashev
- M. V. Lomonosov Moscow State University, Department of Biology, Leninskie gory, 1, Moscow 119234, Russia
| | - Sergey A Siletsky
- Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russian Federation.
| | - Eleonora S Imasheva
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
| | - Jennifer M Wang
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
| | - Mahir D Mamedov
- Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russian Federation
| | - Elena A Kryukova
- Shemyakin & Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya, 16/10, Moscow 117997, Russia; Emanuel Institute of Biochemical Physics, Kosygina str., 4, Moscow 119334, Russia
| | - Dmitriy A Dolgikh
- Shemyakin & Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya, 16/10, Moscow 117997, Russia; M. V. Lomonosov Moscow State University, Department of Biology, Leninskie gory, 1, Moscow 119234, Russia; Emanuel Institute of Biochemical Physics, Kosygina str., 4, Moscow 119334, Russia
| | - Andrei B Rubin
- M. V. Lomonosov Moscow State University, Department of Biology, Leninskie gory, 1, Moscow 119234, Russia
| | - Mikhail P Kirpichnikov
- Shemyakin & Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya, 16/10, Moscow 117997, Russia; M. V. Lomonosov Moscow State University, Department of Biology, Leninskie gory, 1, Moscow 119234, Russia
| | - Sergei P Balashov
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
| | - Janos K Lanyi
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
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8
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Boll LB, Raines RT. Context‐dependence of the Reactivity of Cysteine and Lysine Residues. Chembiochem 2022; 23:e202200258. [PMID: 35527228 PMCID: PMC9308718 DOI: 10.1002/cbic.202200258] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Indexed: 11/11/2022]
Abstract
The S‐alkylation of Cys residues with a maleimide and the Nϵ‐acylation of Lys residues with an N‐hydroxysuccinimide (NHS) ester are common methods for bioconjugation. Using Cys and Lys derivatives as proxies, we assessed differences in reactivity depending on the position of Cys or Lys in a protein sequence. We find that Cys position is exploitable to improve site‐selectivity in maleimide‐based modifications. Reactivity decreases substantially in the order N‐terminal>in‐chain>C‐terminal Cys due to modulation of sulfhydryl pKa by the α‐ammonium and carboxylate groups at the termini. A lower pKa value yields a larger fraction thiolate, which promotes selectivity while somewhat decreasing thiolate nucleophilicity in accord with βnuc
=0.41. Lowering pH and salt concentration enhances selectivity still further. In contrast, differences in the reactivity of Lys towards an NHS ester were modest due to an appreciable decrease in amino group nucleophilicity with a lower pKa of its conjugate acid. Hence, site‐selective Lys modification protocols will require electrophiles other than NHS esters.
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Affiliation(s)
- Linus B. Boll
- Massachusetts Institute of Technology Department of Chemistry 77 Massachusetts Avenue 02139 Cambridge UNITED STATES
| | - Ronald T. Raines
- Massachusetts Institute of Technology Department of Chemistry 77 Massachusetts Avenue, 18-498 02139-4307 Cambridge UNITED STATES
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9
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Rindfleisch S, Krull M, Uranga J, Schmidt T, Rabe von Pappenheim F, Kirck LL, Balouri A, Schneider T, Chari A, Kluger R, Bourenkov G, Diederichsen U, Mata RA, Tittmann K. Ground-state destabilization by electrostatic repulsion is not a driving force in orotidine-5′-monophosphate decarboxylase catalysis. Nat Catal 2022. [DOI: 10.1038/s41929-022-00771-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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10
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Flaiz M, Ludwig G, Bengelsdorf FR, Dürre P. Production of the biocommodities butanol and acetone from methanol with fluorescent FAST-tagged proteins using metabolically engineered strains of Eubacterium limosum. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:117. [PMID: 33971948 PMCID: PMC8111989 DOI: 10.1186/s13068-021-01966-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 04/29/2021] [Indexed: 05/12/2023]
Abstract
BACKGROUND The interest in using methanol as a substrate to cultivate acetogens increased in recent years since it can be sustainably produced from syngas and has the additional benefit of reducing greenhouse gas emissions. Eubacterium limosum is one of the few acetogens that can utilize methanol, is genetically accessible and, therefore, a promising candidate for the recombinant production of biocommodities from this C1 carbon source. Although several genetic tools are already available for certain acetogens including E. limosum, the use of brightly fluorescent reporter proteins is still limited. RESULTS In this study, we expanded the genetic toolbox of E. limosum by implementing the fluorescence-activating and absorption shifting tag (FAST) as a fluorescent reporter protein. Recombinant E. limosum strains that expressed the gene encoding FAST in an inducible and constitutive manner were constructed. Cultivation of these recombinant strains resulted in brightly fluorescent cells even under anaerobic conditions. Moreover, we produced the biocommodities butanol and acetone from methanol with recombinant E. limosum strains. Therefore, we used E. limosum cultures that produced FAST-tagged fusion proteins of the bifunctional acetaldehyde/alcohol dehydrogenase or the acetoacetate decarboxylase, respectively, and determined the fluorescence intensity and product concentrations during growth. CONCLUSIONS The addition of FAST as an oxygen-independent fluorescent reporter protein expands the genetic toolbox of E. limosum. Moreover, our results show that FAST-tagged fusion proteins can be constructed without negatively impacting the stability, functionality, and productivity of the resulting enzyme. Finally, butanol and acetone can be produced from methanol using recombinant E. limosum strains expressing genes encoding fluorescent FAST-tagged fusion proteins.
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Affiliation(s)
- Maximilian Flaiz
- Institute of Microbiology and Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
| | - Gideon Ludwig
- Institute of Microbiology and Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Frank R Bengelsdorf
- Institute of Microbiology and Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Peter Dürre
- Institute of Microbiology and Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
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11
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Uranga J, Hasecke L, Proppe J, Fingerhut J, Mata RA. Theoretical Studies of the Acid-Base Equilibria in a Model Active Site of the Human 20S Proteasome. J Chem Inf Model 2021; 61:1942-1953. [PMID: 33719420 DOI: 10.1021/acs.jcim.0c01459] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The 20S proteasome is a macromolecule responsible for the chemical step in the ubiquitin-proteasome system of degrading unnecessary and unused proteins of the cell. It plays a central role both in the rapid growth of cancer cells and in viral infection cycles. Herein, we present a computational study of the acid-base equilibria in an active site of the human proteasome (caspase-like), an aspect which is often neglected despite the crucial role protons play in the catalysis. As example substrates, we take the inhibition by epoxy- and boronic acid-containing warheads. We have combined cluster quantum mechanical calculations, replica exchange molecular dynamics, and Bayesian optimization of nonbonded potential terms in the inhibitors. In relation to the latter, we propose an easily scalable approach for the reevaluation of nonbonded potentials making use of the hybrid quantum mechanics molecular mechanics dynamics information. Our results show that coupled acid-base equilibria need to be considered when modeling the inhibition mechanism. The coupling between a neighboring lysine and the reacting threonine is not affected by the presence of the studied inhibitors.
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Affiliation(s)
- Jon Uranga
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Lukas Hasecke
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Jonny Proppe
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Jan Fingerhut
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Ricardo A Mata
- Institute of Physical Chemistry, University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
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12
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Sarkar A, Roitberg AE. pH-Dependent Conformational Changes Lead to a Highly Shifted p Ka for a Buried Glutamic Acid Mutant of SNase. J Phys Chem B 2020; 124:11072-11080. [PMID: 33259714 DOI: 10.1021/acs.jpcb.0c07136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ionizable residues are rarely present in the hydrophobic interior of proteins, but when they are, they play important roles in biological processes such as energy transduction and enzyme catalysis. Internal ionizable residues have anomalous experimental pKa values with respect to their pKa in bulk water. This work investigates the atomistic cause of the highly shifted pKa of the internal Glu23 in the artificially mutated variant V23E of Staphylococcal Nuclease (SNase) using pH replica exchange molecular dynamics (pH-REMD) simulations. The pKa of Glu23 obtained from our calculations is 6.55, which is elevated with respect to the glutamate pKa of 4.40 in bulk water. The calculated value is close to the experimental pKa of 7.10. Our simulations show that the highly shifted pKa of Glu23 is the product of a pH-dependent conformational change, which has been observed experimentally and also seen in our simulations. We carry out an analysis of this pH-dependent conformational change in response to the protonation state change of Glu23. Using a four-state thermodynamic model, we estimate the two conformation-specific pKa values of Glu23 and describe the coupling between the conformational and ionization equilibria.
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Affiliation(s)
- Ankita Sarkar
- Department of Physics, University of Florida, Gainesville, Florida 32611, United States
| | - Adrian E Roitberg
- Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
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13
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Straub CT, Bing RG, Otten JK, Keller LM, Zeldes BM, Adams MWW, Kelly RM. Metabolically engineered Caldicellulosiruptor bescii as a platform for producing acetone and hydrogen from lignocellulose. Biotechnol Bioeng 2020; 117:3799-3808. [PMID: 32770740 DOI: 10.1002/bit.27529] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 07/12/2020] [Accepted: 08/05/2020] [Indexed: 11/10/2022]
Abstract
The production of volatile industrial chemicals utilizing metabolically engineered extreme thermophiles offers the potential for processes with simultaneous fermentation and product separation. An excellent target chemical for such a process is acetone (Tb = 56°C), ideally produced from lignocellulosic biomass. Caldicellulosiruptor bescii (Topt 78°C), an extremely thermophilic fermentative bacterium naturally capable of deconstructing and fermenting lignocellulose, was metabolically engineered to produce acetone. When the acetone pathway construct was integrated into a parent strain containing the bifunctional alcohol dehydrogenase from Clostridium thermocellum, acetone was produced at 9.1 mM (0.53 g/L), in addition to minimal ethanol 3.3 mM (0.15 g/L), along with net acetate consumption. This demonstrates that C. bescii can be engineered with balanced pathways in which renewable carbohydrate sources are converted to useful metabolites, primarily acetone and H2 , without net production of its native fermentation products, acetate and lactate.
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Affiliation(s)
- Christopher T Straub
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
| | - Ryan G Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
| | - Jonathan K Otten
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
| | - Lisa M Keller
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
| | - Benjamin M Zeldes
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
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14
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Motojima F, Izumi A, Nuylert A, Zhai Z, Dadashipour M, Shichida S, Yamaguchi T, Nakano S, Asano Y. R-hydroxynitrile lyase from the cyanogenic millipede, Chamberlinius hualienensis-A new entry to the carrier protein family Lipocalines. FEBS J 2020; 288:1679-1695. [PMID: 32679618 PMCID: PMC7983990 DOI: 10.1111/febs.15490] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 06/30/2020] [Accepted: 07/08/2020] [Indexed: 01/05/2023]
Abstract
Hydroxynitrile lyases (HNLs) catalyze the cleavage of cyanohydrin into cyanide and the corresponding aldehyde or ketone. Moreover, they catalyze the synthesis of cyanohydrin in the reverse reaction, utilized in industry for preparation of enantiomeric pure pharmaceutical ingredients and fine chemicals. We discovered a new HNL from the cyanogenic millipede, Chamberlinius hualienensis. The enzyme displays several features including a new primary structure, high stability, and the highest specific activity in (R)‐mandelonitrile ((R)‐MAN) synthesis (7420 U·mg−1) among the reported HNLs. In this study, we elucidated the crystal structure and reaction mechanism of natural ChuaHNL in ligand‐free form and its complexes with acetate, cyanide ion, and inhibitors (thiocyanate or iodoacetate) at 1.6, 1.5, 2.1, 1.55, and 1.55 Å resolutions, respectively. The structure of ChuaHNL revealed that it belongs to the lipocalin superfamily, despite low amino acid sequence identity. The docking model of (R)‐MAN with ChuaHNL suggested that the hydroxyl group forms hydrogen bonds with R38 and K117, and the nitrile group forms hydrogen bonds with R38 and Y103. The mutational analysis showed the importance of these residues in the enzymatic reaction. From these results, we propose that K117 acts as a base to abstract a proton from the hydroxyl group of cyanohydrins and R38 acts as an acid to donate a proton to the cyanide ion during the cleavage reaction of cyanohydrins. The reverse mechanism would occur during the cyanohydrin synthesis. (Photo: Dr. Yuko Ishida) Databases Structural data are available in PDB database under the accession numbers 6JHC, 6KFA, 6KFB, 6KFC, and 6KFD.
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Affiliation(s)
- Fumihiro Motojima
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, Imizu, Toyama, Japan.,Asano Active Enzyme Molecule Project, ERATO, JST, Imizu, Toyama, 939-0398, Japan
| | - Atsushi Izumi
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, Imizu, Toyama, Japan.,Asano Active Enzyme Molecule Project, ERATO, JST, Imizu, Toyama, 939-0398, Japan
| | - Aem Nuylert
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, Imizu, Toyama, Japan
| | - Zhenyu Zhai
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, Imizu, Toyama, Japan.,Asano Active Enzyme Molecule Project, ERATO, JST, Imizu, Toyama, 939-0398, Japan
| | - Mohammad Dadashipour
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, Imizu, Toyama, Japan.,Asano Active Enzyme Molecule Project, ERATO, JST, Imizu, Toyama, 939-0398, Japan
| | - Sayaka Shichida
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, Imizu, Toyama, Japan.,Asano Active Enzyme Molecule Project, ERATO, JST, Imizu, Toyama, 939-0398, Japan
| | - Takuya Yamaguchi
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, Imizu, Toyama, Japan.,Asano Active Enzyme Molecule Project, ERATO, JST, Imizu, Toyama, 939-0398, Japan
| | - Shogo Nakano
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, Imizu, Toyama, Japan.,Asano Active Enzyme Molecule Project, ERATO, JST, Imizu, Toyama, 939-0398, Japan
| | - Yasuhisa Asano
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, Imizu, Toyama, Japan.,Asano Active Enzyme Molecule Project, ERATO, JST, Imizu, Toyama, 939-0398, Japan
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15
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Habe H, Sato Y, Kirimura K. Microbial and enzymatic conversion of levulinic acid, an alternative building block to fermentable sugars from cellulosic biomass. Appl Microbiol Biotechnol 2020; 104:7767-7775. [PMID: 32770274 DOI: 10.1007/s00253-020-10813-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/25/2020] [Accepted: 08/02/2020] [Indexed: 12/16/2022]
Abstract
Levulinic acid (LA) is an important chemical building block listed among the top 12 value-added chemicals by the United States Department of Energy, and can be obtained through the hydrolysis of lignocellulosic biomass. Using the same approach as in the catalytic production of LA from biomass, catalytic methods to upgrade LA to higher value chemicals have been investigated. Since the discovery of the catabolic genes and enzymes in the LA metabolic pathway, bioconversion of LA into useful chemicals has attracted attention, and can potentially broaden the range of biochemical products derived from cellulosic biomass. With a brief introduction to the LA catabolic pathway in Pseudomonas spp., this review summarizes the current studies on the microbial conversion of LA into bioproducts, including the recent developments to achieve higher yields through genetic engineering of Escherichia coli cells. Three different types of reactions during the enzymatic conversion of LA are also discussed. KEY POINTS: • Levulinic acid is an alternative building block to sugars from cellulosic biomass. • Introduction of levulinic acid bioconversion with natural and engineered microbes. • Initial enzymatic conversion of levulinic acid proceeds via three different pathways. • 4-Hydroxyvalerate is one of the target chemicals for levulinic acid bioconversion.
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Affiliation(s)
- Hiroshi Habe
- Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569, Japan.
| | - Yuya Sato
- Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569, Japan
| | - Kohtaro Kirimura
- Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, Tokyo, 169-8555, Japan
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16
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Hiller DA, Dunican BF, Nallur S, Li NS, Piccirilli JA, Strobel SA. The Positively Charged Active Site of the Bacterial Toxin RelE Causes a Large Shift in the General Base p Ka. Biochemistry 2020; 59:1665-1671. [PMID: 32320214 DOI: 10.1021/acs.biochem.9b01047] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The bacterial toxin RelE cleaves mRNA in the ribosomal A site. Although it shares a global fold with other microbial RNases, the active site contains several positively charged residues instead of histidines and glutamates that are typical of ribonucleases. The pH dependences of wild-type and mutant RelE indicate it uses general acid-base catalysis, but either the general acid (proposed to be R81) or the general base must have a substantially downshifted pKa. However, which group is shifted cannot be determined using available structural and biochemical data. Here, we use a phosphorothiolate at the scissile phosphate to remove the need for a general acid. We show this modification rescues nearly all of the defect of the R81A mutation, supporting R81 as the general acid. We also find that the observed pKa of the general base is dependent on the charge of the side chain at position 81. This indicates that positive charge in the active site contributes to a general base pKa downshifted by more than 5 units. Although this modestly reduces the effectiveness of general acid-base catalysis, it is strongly supplemented by the role of the positive charge in stabilizing the transition state for cleavage. Furthermore, we show that the ribosome is required for cleavage but not binding of mRNA by RelE. Ribosome functional groups do not directly contact the scissile phosphate, indicating that positioning and charge interactions dominate RelE catalysis. The unusual RelE active site catalyzes phosphoryl transfer at a rate comparable to those of similar enzymes, but in a ribosome-dependent fashion.
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Affiliation(s)
- David A Hiller
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Chemistry and Chemical Biology Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Brian F Dunican
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Sunitha Nallur
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Chemistry and Chemical Biology Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Nan-Sheng Li
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Joseph A Piccirilli
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Scott A Strobel
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Chemistry and Chemical Biology Institute, Yale University, West Haven, Connecticut 06516, United States
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17
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Viola RE. The ammonia-lyases: enzymes that use a wide range of approaches to catalyze the same type of reaction. Crit Rev Biochem Mol Biol 2020; 54:467-483. [PMID: 31906712 DOI: 10.1080/10409238.2019.1708261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The paradigm that protein structure determines protein function has been clearly established. What is less clear is whether a specific protein structure is always required to carry out a specific function. Numerous cases are now known where there is no apparent connection between the biological function of a protein and the other members of its structural class, and where functionally related proteins can have quite diverse structures. A set of enzymes with these diverse properties, the ammonia-lyases, will be examined in this review. These are a class of enzymes that catalyze a relatively straightforward deamination reaction. However, the individual enzymes of this class possess a wide variety of different structures, utilize a diverse set of cofactors, and appear to catalyze this related reaction through a range of different mechanisms. This review aims to address a basic question: if there is not a specific protein structure and active site architecture that is both required and sufficient to define a catalyst for a given chemical reaction, then what factor(s) determine the structure and the mechanism that is selected to catalyze a particular reaction?
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Affiliation(s)
- Ronald E Viola
- Department of Chemistry and Biochemistry, University of Toledo, Toledo, OH, USA
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18
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Mydy LS, Hoppe RW, Hagemann TM, Schwabacher AW, Silvaggi NR. Mechanistic Studies of the Streptomyces bingchenggensis Aldolase-Dehydratase: Implications for Substrate and Reaction Specificity in the Acetoacetate Decarboxylase-like Superfamily. Biochemistry 2019; 58:4136-4147. [PMID: 31524380 DOI: 10.1021/acs.biochem.9b00652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The acetoacetate decarboxylase-like superfamily (ADCSF) is a little-explored group of enzymes that may contain new biocatalysts. The low level of sequence identity (∼20%) between many ADCSF enzymes and the confirmed acetoacetate decarboxylases led us to investigate the degree of diversity in the reaction and substrate specificity of ADCSF enzymes. We have previously reported on Sbi00515, which belongs to Family V of the ADCSF and functions as an aldolase-dehydratase. Here, we more thoroughly characterize the substrate specificity of Sbi00515 and find that aromatic, unsaturated aldehydes yield lower KM and higher kcat values compared to those of other small electrophilic substrates in the condensation reaction. The roles of several active site residues were explored by site-directed mutagenesis and steady state kinetics. The lysine-glutamate catalytic dyad, conserved throughout the ADCSF, is required for catalysis. Tyrosine 252, which is unique to Sbi00515, is hypothesized to orient the incoming aldehyde in the condensation reaction. Transient state kinetics and an intermediate-bound crystal structure aid in completing a proposed mechanism for Sbi00515.
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Affiliation(s)
- Lisa S Mydy
- Department of Chemistry and Biochemistry , University of Wisconsin-Milwaukee , 3210 North Cramer Street , Milwaukee , Wisconsin 53211 , United States
| | - Robert W Hoppe
- Department of Chemistry and Biochemistry , University of Wisconsin-Milwaukee , 3210 North Cramer Street , Milwaukee , Wisconsin 53211 , United States
| | - Trevor M Hagemann
- Department of Chemistry and Biochemistry , University of Wisconsin-Milwaukee , 3210 North Cramer Street , Milwaukee , Wisconsin 53211 , United States
| | - Alan W Schwabacher
- Department of Chemistry and Biochemistry , University of Wisconsin-Milwaukee , 3210 North Cramer Street , Milwaukee , Wisconsin 53211 , United States
| | - Nicholas R Silvaggi
- Department of Chemistry and Biochemistry , University of Wisconsin-Milwaukee , 3210 North Cramer Street , Milwaukee , Wisconsin 53211 , United States
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19
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Lubkowski J, Wlodawer A. Geometric considerations support the double-displacement catalytic mechanism of l-asparaginase. Protein Sci 2019; 28:1850-1864. [PMID: 31423681 PMCID: PMC6740147 DOI: 10.1002/pro.3709] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/13/2019] [Accepted: 08/13/2019] [Indexed: 11/09/2022]
Abstract
Twenty crystal structures of the complexes of l-asparaginase with l-Asn, l-Asp, and succinic acid that are currently available in the Protein Data Bank, as well as 11 additional structures determined in the course of this project, were analyzed in order to establish the level of conservation of the geometric parameters describing interactions between the substrates and the active site of the enzymes. We found that such stereochemical relationships are highly conserved, regardless of the organism from which the enzyme was isolated, specific crystallization conditions, or the nature of the ligands. Analysis of the geometry of the interactions, including Bürgi-Dunitz and Flippin-Lodge angles, indicated that Thr12 (Escherichia coli asparaginase II numbering) is optimally placed to be the primary nucleophile in the most likely scenario utilizing a double-displacement mechanism, whereas catalysis through a single-displacement mechanism appears to be the least likely.
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Affiliation(s)
- Jacek Lubkowski
- Macromolecular Crystallography LaboratoryNational Cancer InstituteFrederickMaryland
| | - Alexander Wlodawer
- Macromolecular Crystallography LaboratoryNational Cancer InstituteFrederickMaryland
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20
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Goryanova B, Amyes TL, Richard JP. Role of the Carboxylate in Enzyme-Catalyzed Decarboxylation of Orotidine 5'-Monophosphate: Transition State Stabilization Dominates Over Ground State Destabilization. J Am Chem Soc 2019; 141:13468-13478. [PMID: 31365243 PMCID: PMC6735427 DOI: 10.1021/jacs.9b04823] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
Kinetic
parameters kex (s–1)
and kex/Kd (M–1 s–1) are reported
for exchange
for deuterium in D2O of the C-6 hydrogen of 5-fluororotidine
5′-monophosphate (FUMP) catalyzed by the Q215A,
Y217F, and Q215A/Y217F variants of yeast orotidine 5′-monophosphate
decarboxylase (ScOMPDC) at pD 8.1, and by the Q215A
variant at pD 7.1–9.3. The pD rate profiles for wildtype ScOMPDC and the Q215A variant are identical, except for
a 2.5 log unit downward displacement in the profile for the Q215A
variant. The Q215A, Y217F and Q215A/Y217F substitutions cause 1.3–2.0
kcal/mol larger increases in the activation barrier for wildtype ScOMPDC-catalyzed deuterium exchange compared with decarboxylation,
because of the stronger apparent side chain interaction with the transition
state for the deuterium exchange reaction. The stabilization of the
transition state for the OMPDC-catalyzed deuterium exchange reaction
of FUMP is ca. 19 kcal/mol smaller than the transition
state for decarboxylation of OMP, and ca. 8 kcal/mol
smaller than for OMPDC-catalyzed deprotonation of FUMP to form the vinyl carbanion intermediate common to OMPDC-catalyzed
reactions OMP/FOMP and UMP/FUMP. We propose
that ScOMPDC shows similar stabilizing interactions
with the common portions of decarboxylation and deprotonation transition
states that lead to formation of this vinyl carbanion intermediate,
and that there is a large ca. (19–8) = 11 kcal/mol stabilization
of the former transition state from interactions with the nascent
CO2 of product. The effects of Q215A and Y217F substitutions
on kcat/Km for decarboxylation of OMP are expressed mainly as
an increase in Km for the reactions catalyzed
by the variant enzymes, while the effects on kex/Kd for deuterium exchange are
expressed mainly as an increase in kex. This shows that the Q215 and Y217 side chains stabilize the Michaelis
complex to OMP for the decarboxylation reaction, compared
with the complex to FUMP for the deuterium exchange reaction.
These results provide strong support for the conclusion that interactions
which stabilize the transition state for ScOMPDC-catalyzed
decarboxylation at a nonpolar enzyme active site dominate over interactions
that destabilize the ground-state Michaelis complex.
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Affiliation(s)
- Bogdana Goryanova
- Department of Chemistry , University at Buffalo, SUNY , Buffalo , New York 14260-3000 , United States
| | - Tina L Amyes
- Department of Chemistry , University at Buffalo, SUNY , Buffalo , New York 14260-3000 , United States
| | - John P Richard
- Department of Chemistry , University at Buffalo, SUNY , Buffalo , New York 14260-3000 , United States
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21
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Yin H, Cheng Q, Rosas R, Viel S, Monnier V, Charles L, Siri D, Gigmes D, Ouari O, Wang R, Kermagoret A, Bardelang D. A Cucurbit[8]uril 2:2 Complex with a Negative pK a Shift. Chemistry 2019; 25:12552-12559. [PMID: 31286592 DOI: 10.1002/chem.201902057] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 06/13/2019] [Indexed: 12/22/2022]
Abstract
A viologen derivative carrying a benzimidazole group (V-P-I 2+ ; viologen-phenylene-imidazole V-P-I) can be dimerized in water using cucurbit[8]uril (CB[8]) in the form of a 2:2 complex resulting in a negative shift of the guest pKa , by more than 1 pH unit, contrasting with the positive pKa shift usually observed for CB-based complexes. Whereas 2:2 complex protonation is unclear by NMR, silver cations have been used for probing the accessibility of the imidazole groups of the 2:2 complexes. The protonation capacity of the buried imidazole groups is reduced, suggesting that CB[8] could trigger proton release upon 2:2 complex formation. The addition of CB[8] to a solution containing V-P- I3+ indeed released protons as monitored by pH-metry and visualized by a coloured indicator. This property was used to induce a host/guest swapping, accompanied by a proton transfer, between V-P-I 3+ ⋅CB[7] and a CB[8] complex of 1-methyl-4-(4-pyridyl)pyridinium. The origin of this negative pKa shift is proposed to stand in an ideal charge state, and in the position of the two pH-responsive fragments inside the two CB[8] which, alike residues engulfed in proteins, favour the deprotonated form of the guest molecules. Such proton release triggered by a recognition event is reminiscent of several biological processes and may open new avenues toward bioinspired enzyme mimics catalyzing proton transfer or chemical reactions.
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Affiliation(s)
- Hang Yin
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Avenida da Universidade, Taipa, Macau, P. R. China
| | - Qian Cheng
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Avenida da Universidade, Taipa, Macau, P. R. China
| | - Roselyne Rosas
- Aix Marseille Univ, CNRS, Spectropole, FR 1739, Marseille, France
| | - Stéphane Viel
- Aix Marseille Univ, CNRS, ICR, Marseille, France.,Institut Universitaire de France, Paris, France
| | - Valérie Monnier
- Aix Marseille Univ, CNRS, Spectropole, FR 1739, Marseille, France
| | | | - Didier Siri
- Aix Marseille Univ, CNRS, ICR, Marseille, France
| | | | | | - Ruibing Wang
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Avenida da Universidade, Taipa, Macau, P. R. China
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22
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Yang Y, Davis I, Matsui T, Rubalcava I, Liu A. Quaternary structure of α-amino-β-carboxymuconate-ϵ-semialdehyde decarboxylase (ACMSD) controls its activity. J Biol Chem 2019; 294:11609-11621. [PMID: 31189654 PMCID: PMC6663868 DOI: 10.1074/jbc.ra119.009035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 06/10/2019] [Indexed: 01/07/2023] Open
Abstract
α-Amino-β-carboxymuconate-ϵ-semialdehyde decarboxylase (ACMSD) plays an important role in l-tryptophan degradation via the kynurenine pathway. ACMSD forms a homodimer and is functionally inactive as a monomer because its catalytic assembly requires an arginine residue from a neighboring subunit. However, how the oligomeric state and self-association of ACMSD are controlled in solution remains unexplored. Here, we demonstrate that ACMSD from Pseudomonas fluorescens can self-assemble into homodimer, tetramer, and higher-order structures. Using size-exclusion chromatography coupled with small-angle X-ray scattering (SEC-SAXS) analysis, we investigated the ACMSD tetramer structure, and fitting the SAXS data with X-ray crystal structures of the monomeric component, we could generate a pseudo-atomic structure of the tetramer. This analysis revealed a tetramer model of ACMSD as a head-on dimer of dimers. We observed that the tetramer is catalytically more active than the dimer and is in equilibrium with the monomer and dimer. Substituting a critical residue of the dimer-dimer interface, His-110, altered the tetramer dissociation profile by increasing the higher-order oligomer portion in solution without changing the X-ray crystal structure. ACMSD self-association was affected by pH, ionic strength, and other electrostatic interactions. Alignment of ACMSD sequences revealed that His-110 is highly conserved in a few bacteria that utilize nitrobenzoic acid as a sole source of carbon and energy, suggesting a dedicated functional role of ACMSD's self-assembly into the tetrameric and higher-order structures. These results indicate that the dynamic oligomerization status potentially regulates ACMSD activity and that SEC-SAXS coupled with X-ray crystallography is a powerful tool for studying protein self-association.
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Affiliation(s)
- Yu Yang
- Department of Chemistry, University of Texas, San Antonio, Texas 78249
| | - Ian Davis
- Department of Chemistry, University of Texas, San Antonio, Texas 78249
| | - Tsutomu Matsui
- Stanford Synchrotron Radiation Light Source, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025
| | - Ivan Rubalcava
- Department of Chemistry, University of Texas, San Antonio, Texas 78249
| | - Aimin Liu
- Department of Chemistry, University of Texas, San Antonio, Texas 78249, To whom correspondence should be addressed. Tel.:
210-458-7062; E-mail:
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23
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Sakipov SN, Flores-Canales JC, Kurnikova MG. A Hierarchical Approach to Predict Conformation-Dependent Histidine Protonation States in Stable and Flexible Proteins. J Phys Chem B 2019; 123:5024-5034. [PMID: 31095377 DOI: 10.1021/acs.jpcb.9b00656] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Solution acidity measured by pH is an important environmental factor that affects protein structure. It influences the protonation state of protein residues, which in turn may be coupled to protein conformational changes, unfolding, and ligand binding. It remains difficult to compute and measure the p Ka of individual residues, as well as to relate them to pH-dependent protein transitions. This paper presents a hierarchical approach to compute the p Ka of individual protonatable residues, specifically histidines, coupled with underlying structural changes of a protein. A fast and efficient free energy perturbation (FEP) algorithm has also been developed utilizing a fast implementation of standard molecular dynamics (MD) algorithms. Specifically, a CUDA version of the AMBER MD engine is used in this paper. Eight histidine p Ka's are computed in a diverse set of pH stable proteins to demonstrate the proposed approach's utility and assess the predictive quality of the AMBER FF99SB force field. A reference molecule is carefully selected and tested for convergence. A hierarchical approach is used to model p Ka's of the six histidine residues of the diphtheria toxin translocation domain (DTT), which exhibits a diverse ensemble of individual conformations and pH-dependent unfolding. The hierarchical approach consists of first sampling equilibrium conformational ensembles of a protein with protonated and neutral histidine residues via long equilibrium MD simulations (Flores-Canales, J. C.; et al. bioRxiv, 2019, 572040). A clustering method is then used to identify sampled protein conformations, and p Ka's of histidines in each protein conformation are computed. Finally, an ensemble averaging formalism is developed to compute weighted average histidine p Ka's. These can be compared with an apparent experimentally measured p Ka of the DTT protein and thus allows us to propose a mechanism of pH-dependent unfolding of the DTT protein.
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Affiliation(s)
- Serzhan N Sakipov
- Chemistry Department , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Jose C Flores-Canales
- Chemistry Department , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Maria G Kurnikova
- Chemistry Department , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
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24
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Sarkar A, Gupta PL, Roitberg AE. pH-Dependent Conformational Changes Due to Ionizable Residues in a Hydrophobic Protein Interior: The Study of L25K and L125K Variants of SNase. J Phys Chem B 2019; 123:5742-5754. [DOI: 10.1021/acs.jpcb.9b03816] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Ankita Sarkar
- Department of Physics, University of Florida, Gainesville, Florida 32611, United States
| | - Pancham Lal Gupta
- Department of Chemistry, University of Florida, Gainesville, Florida 32603, United States
| | - Adrian E. Roitberg
- Department of Chemistry, University of Florida, Gainesville, Florida 32603, United States
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25
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Walsh CT. Biologically generated carbon dioxide: nature's versatile chemical strategies for carboxy lyases. Nat Prod Rep 2019; 37:100-135. [PMID: 31074473 DOI: 10.1039/c9np00015a] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Covering: up to 2019Metabolic production of CO2 is natural product chemistry on a mammoth scale. Just counting humans, among all other respiring organisms, the seven billion people on the planet exhale about 3 billion tons of CO2 per year. Essentially all of the biogenic CO2 arises by action of discrete families of decarboxylases. The mechanistic routes to CO2 release from carboxylic acid metabolites vary with the electronic demands and structures of specific substrates and illustrate the breadth of chemistry employed for C-COO (C-C bond) disconnections. Most commonly decarboxylated are α-keto acid and β-keto acid substrates, the former requiring thiamin-PP as cofactor, the latter typically cofactor-free. The extensive decarboxylation of amino acids, e.g. to neurotransmitter amines, is synonymous with the coenzyme form of vitamin B6, pyridoxal-phosphate, although covalent N-terminal pyruvamide residues serve in some amino acid decarboxylases. All told, five B vitamins (B1, B2, B3, B6, B7), ATP, S-adenosylmethionine, manganese and zinc ions are pressed into service for specific decarboxylase catalyses. There are additional cofactor-independent decarboxylases that operate by distinct chemical routes. Finally, while most decarboxylases use heterolytic ionic mechanisms, a small number of decarboxylases carry out radical pathways.
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26
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Catalytic mechanism for the conversion of salicylate into catechol by the flavin-dependent monooxygenase salicylate hydroxylase. Int J Biol Macromol 2019; 129:588-600. [DOI: 10.1016/j.ijbiomac.2019.01.135] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 01/24/2019] [Accepted: 01/24/2019] [Indexed: 11/17/2022]
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27
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Fetter CM, Morrison ZA, Nagar M, Douglas CD, Bearne SL. Altering the Y137-K164-K166 triad of mandelate racemase and its effect on the observed pK a of the Brønsted base catalysts. Arch Biochem Biophys 2019; 666:116-126. [PMID: 30935886 DOI: 10.1016/j.abb.2019.03.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 03/16/2019] [Accepted: 03/25/2019] [Indexed: 11/16/2022]
Abstract
Mandelate racemase (MR) catalyzes the interconversion of the enantiomers of mandelate using a two-base mechanism with Lys 166 acting as the Brønsted base to abstract the α-proton from (S)-mandelate. The resulting intermediate is subsequently re-protonated by the conjugate acid of His 297 to yield (R)-mandelate. The roles of these amino acids are reversed when (R)-mandelate is the substrate. The side chains of Tyr 137, Lys 164, and Lys 166 form a H-bonding network and the proximity of the two ε-NH3+ groups is believed to lower the pKa of Lys 166. We used site-directed mutagenesis, kinetics, and pH-rate studies to explore the roles of Lys 164 (K164 C/M) and Tyr 137 (Y137 L/F/S/T) in catalysis. The efficiency (kcat/Km) was reduced ∼3.5 × 105-fold for K164C MR, relative to wild-type MR, indicating a major role for this residue in catalysis. The efficiency of Y137F MR, however, was reduced only 25-30-fold. pH-Rate profiles (log kcat vs. pH) revealed that substitution of Tyr 137 by Phe increased the kinetic pKa of Lys 166 from 5.88 ± 0.02 to 7.3 ± 0.2. Hence, Tyr 137 plays an important role in facilitating the reduction of the pKa of the Brønsted base Lys 166 by ∼1.4 units. Interestingly, the Phe substitution also increased the kinetic pKa of His 297 from 5.97 ± 0.04 to 7.1 ± 0.1. Thus, the Tyr 137-Lys 164-Lys 166 H-bonding network plays a broader role in modulating the pKa of catalytic residues by influencing the electrostatic character of the entire active site, not only by decreasing the observed pKa value of Lys 166, but also by decreasing the pKa of His 297 by 1.1 units.
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Affiliation(s)
- Christopher M Fetter
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Zachary A Morrison
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Mitesh Nagar
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Colin D Douglas
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Stephen L Bearne
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, B3H 4R2, Canada; Department of Chemistry, Dalhousie University, Halifax, NS, B3H 4R2, Canada.
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28
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Zeldes BM, Straub CT, Otten JK, Adams MW, Kelly RM. A synthetic enzymatic pathway for extremely thermophilic acetone production based on the unexpectedly thermostable acetoacetate decarboxylase from Clostridium acetobutylicum. Biotechnol Bioeng 2018; 115:2951-2961. [PMID: 30199090 PMCID: PMC6231964 DOI: 10.1002/bit.26829] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 08/25/2018] [Accepted: 09/05/2018] [Indexed: 01/02/2023]
Abstract
One potential advantage of an extremely thermophilic metabolic engineering host (T opt ≥ 70°C) is facilitated recovery of volatile chemicals from the vapor phase of an active fermenting culture. This process would reduce purification costs and concomitantly alleviate toxicity to the cells by continuously removing solvent fermentation products such as acetone or ethanol, a process we are calling "bio-reactive distillation." Although extremely thermophilic heterologous metabolic pathways can be inspired by existing mesophilic versions, they require thermostable homologs of the constituent enzymes if they are to be utilized in extremely thermophilic bacteria or archaea. Production of acetone from acetyl-CoA and acetate in the mesophilic bacterium Clostridium acetobutylicum utilizes three enzymes: thiolase, acetoacetyl-CoA: acetate CoA transferase (CtfAB), and acetoacetate decarboxylase (Adc). Previously reported biocatalytic pathways for acetone production were demonstrated only as high as 55°C. Here, we demonstrate a synthetic enzymatic pathway for acetone production that functions up to at least 70°C in vitro, made possible by the unusual thermostability of Adc from the mesophile C. acetobutylicum, and heteromultimeric acetoacetyl-CoA:acetate CoA-transferase (CtfAB) complexes from Thermosipho melanesiensis and Caldanaerobacter subterraneus, composed of a highly thermostable α-subunit and a thermally labile β-subunit. The three enzymes produce acetone in vitro at temperatures of at least 70°C, paving the way for bio-reactive distillation of acetone using a metabolically engineered extreme thermophile as a production host.
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Affiliation(s)
- Benjamin M. Zeldes
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| | - Christopher T. Straub
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| | - Jonathan K. Otten
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| | - Michael W.W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
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29
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Abstract
The concept of cell signaling in the context of nonenzyme-assisted protein modifications by reactive electrophilic and oxidative species, broadly known as redox signaling, is a uniquely complex topic that has been approached from numerous different and multidisciplinary angles. Our Review reflects on five aspects critical for understanding how nature harnesses these noncanonical post-translational modifications to coordinate distinct cellular activities: (1) specific players and their generation, (2) physicochemical properties, (3) mechanisms of action, (4) methods of interrogation, and (5) functional roles in health and disease. Emphasis is primarily placed on the latest progress in the field, but several aspects of classical work likely forgotten/lost are also recollected. For researchers with interests in getting into the field, our Review is anticipated to function as a primer. For the expert, we aim to stimulate thought and discussion about fundamentals of redox signaling mechanisms and nuances of specificity/selectivity and timing in this sophisticated yet fascinating arena at the crossroads of chemistry and biology.
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Affiliation(s)
- Saba Parvez
- Department of Pharmacology and Toxicology, College of
Pharmacy, University of Utah, Salt Lake City, Utah, 84112, USA
- Department of Chemistry and Chemical Biology, Cornell
University, Ithaca, New York, 14853, USA
| | - Marcus J. C. Long
- Department of Chemistry and Chemical Biology, Cornell
University, Ithaca, New York, 14853, USA
| | - Jesse R. Poganik
- Ecole Polytechnique Fédérale de Lausanne,
Institute of Chemical Sciences and Engineering, 1015, Lausanne, Switzerland
- Department of Chemistry and Chemical Biology, Cornell
University, Ithaca, New York, 14853, USA
| | - Yimon Aye
- Ecole Polytechnique Fédérale de Lausanne,
Institute of Chemical Sciences and Engineering, 1015, Lausanne, Switzerland
- Department of Chemistry and Chemical Biology, Cornell
University, Ithaca, New York, 14853, USA
- Department of Biochemistry, Weill Cornell Medicine, New
York, New York, 10065, USA
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30
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Hoshino Y, Jibiki T, Nakamoto M, Miura Y. Reversible p K a Modulation of Carboxylic Acids in Temperature-Responsive Nanoparticles through Imprinted Electrostatic Interactions. ACS APPLIED MATERIALS & INTERFACES 2018; 10:31096-31105. [PMID: 30148598 DOI: 10.1021/acsami.8b11397] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The acid dissociation constants (p Ka values) of Brønsted acids at the active sites of proteins are reversibly modulated by intramolecular electrostatic interactions with neighboring ions in a reaction cycle. The resulting p Ka shift is crucial for the proteins to capture, transfer, and release target ions. On the other hand, reversible p Ka modulation through electrostatic interactions in synthetic polymer materials has seldom been realized because the interactions are strongly shielded by solvation water molecules in aqueous media. Here, we prepared hydrogel nanoparticles (NPs) bearing carboxylic acid groups whose p Ka values can be reversibly modulated by electrostatic interactions with counterions in the particles. We found that the deprotonated states of the acids were stabilized by electrostatic interactions with countercations only when the acids and cations were both imprinted in hydrophobic microdomains in the NPs during polymerization. Cationic monomers, like primary amine- and guanidium group-containing monomers, which interacted strongly with growing NPs showed greater p Ka modulation than monomers that did not interact with the NPs, such as quaternary ammonium group-containing monomers. Modulation was enhanced when the guanidium moieties were protected with hydrophobic groups during polymerization, so that the guanidium ions were imprinted in the hydrophobic microdomains; the lowest p Ka of ∼4.0 was achieved as a result. The p Ka modulation of the acids could be reversibly removed by inducing a temperature-dependent volume phase transition of the gel NPs. These design principles are applicable to other stimuli-responsive materials and integral to the development of synthetic materials that can be used to capture, transport, and separate target ions.
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Affiliation(s)
- Yu Hoshino
- Department of Chemical Engineering , Kyushu University , 744 Motooka , Nishi-ku, Fukuoka 819-0395 , Japan
| | - Toshiki Jibiki
- Department of Chemical Engineering , Kyushu University , 744 Motooka , Nishi-ku, Fukuoka 819-0395 , Japan
| | - Masahiko Nakamoto
- Department of Chemical Engineering , Kyushu University , 744 Motooka , Nishi-ku, Fukuoka 819-0395 , Japan
| | - Yoshiko Miura
- Department of Chemical Engineering , Kyushu University , 744 Motooka , Nishi-ku, Fukuoka 819-0395 , Japan
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31
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Kougentakis CM, Grasso EM, Robinson AC, Caro JA, Schlessman JL, Majumdar A, García-Moreno E B. Anomalous Properties of Lys Residues Buried in the Hydrophobic Interior of a Protein Revealed with 15N-Detect NMR Spectroscopy. J Phys Chem Lett 2018; 9:383-387. [PMID: 29266956 DOI: 10.1021/acs.jpclett.7b02668] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Ionizable residues buried in hydrophobic environments in proteins are essential for many fundamental biochemical processes. These residues titrate with anomalous pKa values that are challenging to reproduce with structure-based calculations owing to the conformational reorganization coupled to their ionization. Detailed characterization of this conformational reorganization is of interest; unfortunately, the properties of buried Lys residues are difficult to study experimentally. Here we demonstrate the utility of 15N NMR spectroscopy to gain insight into the protonation state, state of hydration and conformational dynamics of the Nζ amino group of buried Lys residues. The experiments were applied to five variants of staphylococcal nuclease, with internal Lys residues that titrate with pKa values ranging from 6.2 to 8.1. Direct detection of buried Lys residues with these NMR spectroscopy methods will enable correlation between thermodynamic and structural data as well as unprecedented examination of how conformational transitions coupled to their ionization affect their pKa values.
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Affiliation(s)
| | | | | | | | - Jamie L Schlessman
- Chemistry Department, United States Naval Academy , 572M Holloway Rd MS 9B, Annapolis, Maryland 21402, United States
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32
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Mydy LS, Mashhadi Z, Knight TW, Fenske T, Hagemann T, Hoppe RW, Han L, Miller TR, Schwabacher AW, Silvaggi NR. Swit_4259, an acetoacetate decarboxylase-like enzyme from Sphingomonas wittichii RW1. Acta Crystallogr F Struct Biol Commun 2017; 73:672-681. [PMID: 29199988 PMCID: PMC5713672 DOI: 10.1107/s2053230x17015862] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 10/31/2017] [Indexed: 11/10/2022] Open
Abstract
The Gram-negative bacterium Sphingomonas wittichii RW1 is notable for its ability to metabolize a variety of aromatic hydrocarbons. Not surprisingly, the S. wittichii genome contains a number of putative aromatic hydrocarbon-degrading gene clusters. One of these includes an enzyme of unknown function, Swit_4259, which belongs to the acetoacetate decarboxylase-like superfamily (ADCSF). Here, it is reported that Swit_4259 is a small (28.8 kDa) tetrameric ADCSF enzyme that, unlike the prototypical members of the superfamily, does not have acetoacetate decarboxylase activity. Structural characterization shows that the tertiary structure of Swit_4259 is nearly identical to that of the true decarboxylases, but there are important differences in the fine structure of the Swit_4259 active site that lead to a divergence in function. In addition, it is shown that while it is a poor substrate, Swit_4259 can catalyze the hydration of 2-oxo-hex-3-enedioate to yield 2-oxo-4-hydroxyhexanedioate. It is also demonstrated that Swit_4259 has pyruvate aldolase-dehydratase activity, a feature that is common to all of the family V ADCSF enzymes studied to date. The enzymatic activity, together with the genomic context, suggests that Swit_4259 may be a hydratase with a role in the metabolism of an as-yet-unknown hydrocarbon. These data have implications for engineering bioremediation pathways to degrade specific pollutants, as well as structure-function relationships within the ADCSF in general.
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Affiliation(s)
- Lisa S. Mydy
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
| | - Zahra Mashhadi
- Clinical Pharmacology Division, Vanderbilt University, TN 37232, USA
| | - T. William Knight
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
| | - Tyler Fenske
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
| | - Trevor Hagemann
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
| | - Robert W. Hoppe
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
| | - Lanlan Han
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
| | - Todd R. Miller
- Joseph J. Zilber School of Public Health, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
| | - Alan W. Schwabacher
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
| | - Nicholas R. Silvaggi
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
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33
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Over expression of GroESL in Cupriavidus necator for heterotrophic and autotrophic isopropanol production. Metab Eng 2017; 42:74-84. [DOI: 10.1016/j.ymben.2017.05.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 03/30/2017] [Accepted: 05/31/2017] [Indexed: 01/09/2023]
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34
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Benchmarking pKa prediction methods for Lys115 in acetoacetate decarboxylase. J Mol Model 2017; 23:155. [DOI: 10.1007/s00894-017-3324-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 03/17/2017] [Indexed: 11/26/2022]
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35
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Rodrigues MJ, Windeisen V, Zhang Y, Guédez G, Weber S, Strohmeier M, Hanes JW, Royant A, Evans G, Sinning I, Ealick SE, Begley TP, Tews I. Lysine relay mechanism coordinates intermediate transfer in vitamin B6 biosynthesis. Nat Chem Biol 2017; 13:290-294. [PMID: 28092359 PMCID: PMC6078385 DOI: 10.1038/nchembio.2273] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 11/11/2016] [Indexed: 11/08/2022]
Abstract
Substrate channeling has emerged as a common mechanism for enzymatic intermediate transfer. A conspicuous gap in knowledge concerns the use of covalent lysine imines in the transfer of carbonyl-group-containing intermediates, despite their wideuse in enzymatic catalysis. Here we show how imine chemistry operates in the transfer of covalent intermediates in pyridoxal 5'-phosphate biosynthesis by the Arabidopsis thaliana enzyme Pdx1. An initial ribose 5-phosphate lysine imine is converted to the chromophoric I320 intermediate, simultaneously bound to two lysine residues and partially vacating the active site, which creates space for glyceraldehyde 3-phosphate to bind. Crystal structures show how substrate binding, catalysis and shuttling are coupled to conformational changes around strand β6 of the Pdx1 (βα)8-barrel. The dual-specificity active site and imine relay mechanism for migration of carbonyl intermediates provide elegant solutions to the challenge of coordinating a complex sequence of reactions that follow a path of over 20 Å between substrate- and product-binding sites.
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Affiliation(s)
- Matthew J Rodrigues
- Biological Sciences, University of Southampton, Southampton, UK
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
| | - Volker Windeisen
- Biological Sciences, University of Southampton, Southampton, UK
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Yang Zhang
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA
| | - Gabriela Guédez
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Stefan Weber
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Marco Strohmeier
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Jeremiah W Hanes
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA
- Pacific Biosciences, Menlo Park, California, USA
| | - Antoine Royant
- Institut de Biologie Structurale, Université Grenoble Alpes, CNRS, CEA, Grenoble, France
- European Synchrotron Radiation Facility, Grenoble, France
| | - Gwyndaf Evans
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
| | - Irmgard Sinning
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Steven E Ealick
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA
| | - Tadhg P Begley
- Department of Chemistry, Texas A&M University, College Station, Texas, USA
| | - Ivo Tews
- Biological Sciences, University of Southampton, Southampton, UK
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
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36
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Wiechert M, Beitz E. Mechanism of formate-nitrite transporters by dielectric shift of substrate acidity. EMBO J 2017; 36:949-958. [PMID: 28250043 DOI: 10.15252/embj.201695776] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 01/25/2017] [Accepted: 01/30/2017] [Indexed: 11/09/2022] Open
Abstract
Bacterial formate-nitrite transporters (FNTs) regulate the metabolic flow of small, weak mono-acids. Recently, the eukaryotic PfFNT was identified as the malaria parasite's lactate transporter and novel drug target. Despite crystal data, central mechanisms of FNT gating and transport remained unclear. Here, we show elucidation of the FNT transport mechanism by single-step substrate protonation involving an invariant lysine in the periplasmic vestibule. Opposing earlier gating hypotheses and electrophysiology reports, quantification of total uptake by radiolabeled substrate indicates a permanently open conformation of the bacterial formate transporter, FocA, irrespective of the pH Site-directed mutagenesis, heavy water effects, mathematical modeling, and simulations of solvation imply a general, proton motive force-driven FNT transport mechanism: Electrostatic attraction of the acid anion into a hydrophobic vestibule decreases substrate acidity and facilitates protonation by the bulk solvent. We define substrate neutralization by proton transfer for transport via a hydrophobic transport path as a general theme of the Amt/Mep/Rh ammonium and formate-nitrite transporters.
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Affiliation(s)
- Marie Wiechert
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Eric Beitz
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Kiel, Germany
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37
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Mathematical modelling of clostridial acetone-butanol-ethanol fermentation. Appl Microbiol Biotechnol 2017; 101:2251-2271. [PMID: 28210797 PMCID: PMC5320022 DOI: 10.1007/s00253-017-8137-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 01/14/2017] [Accepted: 01/16/2017] [Indexed: 12/24/2022]
Abstract
Clostridial acetone-butanol-ethanol (ABE) fermentation features a remarkable shift in the cellular metabolic activity from acid formation, acidogenesis, to the production of industrial-relevant solvents, solventogensis. In recent decades, mathematical models have been employed to elucidate the complex interlinked regulation and conditions that determine these two distinct metabolic states and govern the transition between them. In this review, we discuss these models with a focus on the mechanisms controlling intra- and extracellular changes between acidogenesis and solventogenesis. In particular, we critically evaluate underlying model assumptions and predictions in the light of current experimental knowledge. Towards this end, we briefly introduce key ideas and assumptions applied in the discussed modelling approaches, but waive a comprehensive mathematical presentation. We distinguish between structural and dynamical models, which will be discussed in their chronological order to illustrate how new biological information facilitates the ‘evolution’ of mathematical models. Mathematical models and their analysis have significantly contributed to our knowledge of ABE fermentation and the underlying regulatory network which spans all levels of biological organization. However, the ties between the different levels of cellular regulation are not well understood. Furthermore, contradictory experimental and theoretical results challenge our current notion of ABE metabolic network structure. Thus, clostridial ABE fermentation still poses theoretical as well as experimental challenges which are best approached in close collaboration between modellers and experimentalists.
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38
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Sugrue E, Carr PD, Scott C, Jackson CJ. Active Site Desolvation and Thermostability Trade-Offs in the Evolution of Catalytically Diverse Triazine Hydrolases. Biochemistry 2016; 55:6304-6313. [DOI: 10.1021/acs.biochem.6b00731] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elena Sugrue
- Research
School of Chemistry, Australian National University, Canberra, Australia
| | - Paul D. Carr
- Research
School of Chemistry, Australian National University, Canberra, Australia
| | | | - Colin J. Jackson
- Research
School of Chemistry, Australian National University, Canberra, Australia
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39
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Abstract
Organophosphonic acids are unique as natural products in terms of stability and mimicry. The C-P bond that defines these compounds resists hydrolytic cleavage, while the phosphonyl group is a versatile mimic of transition-states, intermediates, and primary metabolites. This versatility may explain why a variety of organisms have extensively explored the use organophosphonic acids as bioactive secondary metabolites. Several of these compounds, such as fosfomycin and bialaphos, figure prominently in human health and agriculture. The enzyme reactions that create these molecules are an interesting mix of chemistry that has been adopted from primary metabolism as well as those with no chemical precedent. Additionally, the phosphonate moiety represents a source of inorganic phosphate to microorganisms that live in environments that lack this nutrient; thus, unusual enzyme reactions have also evolved to cleave the C-P bond. This review is a comprehensive summary of the occurrence and function of organophosphonic acids natural products along with the mechanisms of the enzymes that synthesize and catabolize these molecules.
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Affiliation(s)
- Geoff P Horsman
- Department of Chemistry and Biochemistry, Wilfrid Laurier University , Waterloo, Ontario N2L 3C5, Canada
| | - David L Zechel
- Department of Chemistry, Queen's University , Kingston, Ontario K7L 3N6, Canada
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40
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Wu X, Lee J, Brooks BR. Origin of pK a Shifts of Internal Lysine Residues in SNase Studied Via Equal-Molar VMMS Simulations in Explicit Water. J Phys Chem B 2016; 121:3318-3330. [PMID: 27700118 DOI: 10.1021/acs.jpcb.6b08249] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Protein internal ionizable groups can exhibit large shifts in pKa values. Although the environment and interaction changes have been extensively studied both experimentally and computationally, direct calculation of pKa values of these internal ionizable groups in explicit water is challenging due to energy barriers in solvent interaction and in conformational transition. The virtual mixture of multiple states (VMMS) method is a new approach designed to study chemical state equilibrium. This method constructs a virtual mixture of multiple chemical states in order to sample the conformational space of all states simultaneously and to avoid crossing energy barriers related to state transition. By applying VMMS to 25 variants of staphylococcal nuclease with lysine residues at internal positions, we obtained the pKa values of these lysine residues and investigated the physics underlining the pKa shifts. Our calculation results agree reasonably well with experimental measurements, validating the VMMS method for pKa calculation and providing molecular details of the protonation equilibrium for protein internal ionizable groups. Based on our analyses of protein conformation relaxation, lysine side chain flexibility, water penetration, and the microenvironment, we conclude that the hydrophobicity of the microenvironment around the lysine side chain (which affects water penetration differently for different protonation states) plays an important role in the pKa shifts.
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Affiliation(s)
- Xiongwu Wu
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health (NIH) , Bethesda, Maryland 20892, United States
| | - Juyong Lee
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health (NIH) , Bethesda, Maryland 20892, United States
| | - Bernard R Brooks
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health (NIH) , Bethesda, Maryland 20892, United States
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Deng Z, Qian Y, Yu Y, Liu G, Hu J, Zhang G, Liu S. Engineering Intracellular Delivery Nanocarriers and Nanoreactors from Oxidation-Responsive Polymersomes via Synchronized Bilayer Cross-Linking and Permeabilizing Inside Live Cells. J Am Chem Soc 2016; 138:10452-66. [DOI: 10.1021/jacs.6b04115] [Citation(s) in RCA: 221] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Zhengyu Deng
- CAS
Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory
for Physical Sciences at the Microscale, iChEM (Collaborative
Innovation Center of Chemistry for Energy Materials), Department of
Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yinfeng Qian
- Department
of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, Anhui 230022, China
| | - Yongqiang Yu
- Department
of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei, Anhui 230022, China
| | - Guhuan Liu
- CAS
Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory
for Physical Sciences at the Microscale, iChEM (Collaborative
Innovation Center of Chemistry for Energy Materials), Department of
Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jinming Hu
- CAS
Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory
for Physical Sciences at the Microscale, iChEM (Collaborative
Innovation Center of Chemistry for Energy Materials), Department of
Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Guoying Zhang
- CAS
Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory
for Physical Sciences at the Microscale, iChEM (Collaborative
Innovation Center of Chemistry for Energy Materials), Department of
Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Shiyong Liu
- CAS
Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory
for Physical Sciences at the Microscale, iChEM (Collaborative
Innovation Center of Chemistry for Energy Materials), Department of
Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
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Iwahara J, Esadze A, Zandarashvili L. Physicochemical Properties of Ion Pairs of Biological Macromolecules. Biomolecules 2015; 5:2435-63. [PMID: 26437440 PMCID: PMC4693242 DOI: 10.3390/biom5042435] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 09/09/2015] [Accepted: 09/11/2015] [Indexed: 11/23/2022] Open
Abstract
Ion pairs (also known as salt bridges) of electrostatically interacting cationic and anionic moieties are important for proteins and nucleic acids to perform their function. Although numerous three-dimensional structures show ion pairs at functionally important sites of biological macromolecules and their complexes, the physicochemical properties of the ion pairs are not well understood. Crystal structures typically show a single state for each ion pair. However, recent studies have revealed the dynamic nature of the ion pairs of the biological macromolecules. Biomolecular ion pairs undergo dynamic transitions between distinct states in which the charged moieties are either in direct contact or separated by water. This dynamic behavior is reasonable in light of the fundamental concepts that were established for small ions over the last century. In this review, we introduce the physicochemical concepts relevant to the ion pairs and provide an overview of the recent advancement in biophysical research on the ion pairs of biological macromolecules.
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Affiliation(s)
- Junji Iwahara
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA.
| | - Alexandre Esadze
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Levani Zandarashvili
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
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Richman DE, Majumdar A, García-Moreno E B. Conformational Reorganization Coupled to the Ionization of Internal Lys Residues in Proteins. Biochemistry 2015; 54:5888-97. [PMID: 26335188 DOI: 10.1021/acs.biochem.5b00522] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ionizable groups buried in the hydrophobic interior of proteins are essential for energy transduction and catalysis. Because the protein interior is usually neither as polar nor as polarizable as water, these groups tend to have anomalous pKa values, and their ionization tends to be coupled to conformational reorganization. To elucidate mechanisms of energy transduction in proteins, it is necessary to understand the structural determinants of the pKa values of these buried groups, including the range and character of the conformational reorganization that the ionization of these buried groups can elicit. The L25K and L125K variants of staphylococcal nuclease (SNase) were used to characterize the diverse types of structural reorganization that can be promoted by the ionization of buried groups. NMR relaxation dispersion and ZZ-exchange experiments were used to identify the locations and measure the time scales and extent of pH-dependent conformational exchange in these two proteins. The buried Lys-25 and Lys-125 residues titrate with pKa of 6.3 and 6.2, respectively. The L25K protein fluctuates between the native state and an ensemble of locally unfolded states on the 400 μs to 7 ms time scale. On the 100 to 500 ms time scale the native state exchanges with a subglobally unfolded state in which the β-barrel is partially reorganized. The equilibrium between the native state and this alternative state is highly pH dependent; at pH values below the pKa of Lys-25 the state with the partially reorganized β-barrel is the dominant state. In contrast, the L125K protein only exhibited pH-independent fluctuation in the microsecond to millisecond time scale in the region near Lys-125. The study illustrates how diverse and how localized the coupling between conformational reorganization and ionization of buried groups can be. The pH-sensitive exchange between the fully native and subglobally or locally unfolded states in time scales well into hundreds of milliseconds will challenge all computational methods for structure-based calculations of pKa values.
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Affiliation(s)
- Daniel E Richman
- Department of Biophysics and ‡Biomolecular NMR Center, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Ananya Majumdar
- Department of Biophysics and ‡Biomolecular NMR Center, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Bertrand García-Moreno E
- Department of Biophysics and ‡Biomolecular NMR Center, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
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Vashishtha AK, West AH, Cook PF. Probing the chemical mechanism of saccharopine reductase from Saccharomyces cerevisiae using site-directed mutagenesis. Arch Biochem Biophys 2015; 584:98-106. [PMID: 26342457 DOI: 10.1016/j.abb.2015.08.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 08/24/2015] [Accepted: 08/29/2015] [Indexed: 10/23/2022]
Abstract
Saccharopine reductase catalyzes the reductive amination of l-α-aminoadipate-δ-semialdehyde with l-glutamate to give saccharopine. Two mechanisms have been proposed for the reductase, one that makes use of enzyme side chains as acid-base catalytic groups, and a second, in which the reaction is catalyzed by enzyme-bound reactants. Site-directed mutagenesis was used to change acid-base candidates in the active site of the reductase to eliminate their ionizable side chain. Thus, the D126A, C154S and Y99F and several double mutant enzymes were prepared. Kinetic parameters in the direction of glutamate formation exhibited modest decreases, inconsistent with the loss of an acid-base catalyst. The pH-rate profiles obtained with all mutant enzymes decrease at low and high pH, suggesting acid and base catalytic groups are still present in all enzymes. Solvent kinetic deuterium isotope effects are all larger than those observed for wild type enzyme, and approximately equal to one another, suggesting the slow step is the same as that of wild type enzyme, a conformational change to open the site and release products (in the direction of saccharopine formation). Overall, the acid-base chemistry is likely catalyzed by bound reactants, with the exception of deprotonation of the α-amine of glutamate, which likely requires an enzyme residue.
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Affiliation(s)
- Ashwani K Vashishtha
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, 3415 Colorado Ave, JCS Biotech Bldg. 530, Boulder, CO 80309, USA
| | - Ann H West
- Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Blvd., Norman, OK 73019, USA.
| | - Paul F Cook
- Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Blvd., Norman, OK 73019, USA.
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Mudgal R, Sandhya S, Chandra N, Srinivasan N. De-DUFing the DUFs: Deciphering distant evolutionary relationships of Domains of Unknown Function using sensitive homology detection methods. Biol Direct 2015; 10:38. [PMID: 26228684 PMCID: PMC4520260 DOI: 10.1186/s13062-015-0069-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 07/20/2015] [Indexed: 12/23/2022] Open
Abstract
Background In the post-genomic era where sequences are being determined at a rapid rate, we are highly reliant on computational methods for their tentative biochemical characterization. The Pfam database currently contains 3,786 families corresponding to “Domains of Unknown Function” (DUF) or “Uncharacterized Protein Family” (UPF), of which 3,087 families have no reported three-dimensional structure, constituting almost one-fourth of the known protein families in search for both structure and function. Results We applied a ‘computational structural genomics’ approach using five state-of-the-art remote similarity detection methods to detect the relationship between uncharacterized DUFs and domain families of known structures. The association with a structural domain family could serve as a start point in elucidating the function of a DUF. Amongst these five methods, searches in SCOP-NrichD database have been applied for the first time. Predictions were classified into high, medium and low- confidence based on the consensus of results from various approaches and also annotated with enzyme and Gene ontology terms. 614 uncharacterized DUFs could be associated with a known structural domain, of which high confidence predictions, involving at least four methods, were made for 54 families. These structure-function relationships for the 614 DUF families can be accessed on-line at http://proline.biochem.iisc.ernet.in/RHD_DUFS/. For potential enzymes in this set, we assessed their compatibility with the associated fold and performed detailed structural and functional annotation by examining alignments and extent of conservation of functional residues. Detailed discussion is provided for interesting assignments for DUF3050, DUF1636, DUF1572, DUF2092 and DUF659. Conclusions This study provides insights into the structure and potential function for nearly 20 % of the DUFs. Use of different computational approaches enables us to reliably recognize distant relationships, especially when they converge to a common assignment because the methods are often complementary. We observe that while pointers to the structural domain can offer the right clues to the function of a protein, recognition of its precise functional role is still ‘non-trivial’ with many DUF domains conserving only some of the critical residues. It is not clear whether these are functional vestiges or instances involving alternate substrates and interacting partners. Reviewers This article was reviewed by Drs Eugene Koonin, Frank Eisenhaber and Srikrishna Subramanian. Electronic supplementary material The online version of this article (doi:10.1186/s13062-015-0069-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Richa Mudgal
- IISc Mathematics Initiative, Indian Institute of Science, Bangalore, 560 012, India.
| | - Sankaran Sandhya
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560 012, India.
| | - Nagasuma Chandra
- Department of Biochemistry, Indian Institute of Science, Bangalore, 560 012, India.
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Mydy LS, Hoppe RW, Ochsenwald JM, Berndt RT, Severin GB, Schwabacher AW, Silvaggi NR. Sbi00515, a Protein of Unknown Function from Streptomyces bingchenggensis, Highlights the Functional Versatility of the Acetoacetate Decarboxylase Scaffold. Biochemistry 2015; 54:3978-88. [PMID: 26039798 DOI: 10.1021/acs.biochem.5b00483] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The acetoacetate decarboxylase-like superfamily (ADCSF) is a group of ~4000 enzymes that, until recently, was thought to be homogeneous in terms of the reaction catalyzed. Bioinformatic analysis shows that the ADCSF consists of up to seven families that differ primarily in their active site architectures. The soil-dwelling bacterium Streptomyces bingchenggensis BCW-1 produces an ADCSF enzyme of unknown function that shares a low level of sequence identity (~20%) with known acetoacetate decarboxylases (ADCs). This enzyme, Sbi00515, belongs to the MppR-like family of the ADCSF because of its similarity to the mannopeptimycin biosynthetic protein MppR from Streptomyces hygroscopicus. Herein, we present steady state kinetic data that show Sbi00515 does not catalyze the decarboxylation of any α- or β-keto acid tested. Rather, we show that Sbi00515 catalyzes the condensation of pyruvate with a number of aldehydes, followed by dehydration of the presumed aldol intermediate. Thus, Sbi00515 is a pyruvate aldolase-dehydratase and not an acetoacetate decarboxylase. We have also determined the X-ray crystal structures of Sbi00515 in complexes with formate and pyruvate. The structures show that the overall fold of Sbi00515 is nearly identical to those of both ADC and MppR. The pyruvate complex is trapped as the Schiff base, providing evidence that the Schiff base chemistry that drives the acetoacetate decarboxylases has been co-opted to perform a new function, and that this core chemistry may be conserved across the superfamily. The structures also suggest possible catalytic roles for several active site residues.
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Affiliation(s)
- Lisa S Mydy
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
| | - Robert W Hoppe
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
| | - Jenna M Ochsenwald
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
| | - Robert T Berndt
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
| | - Geoffrey B Severin
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
| | - Alan W Schwabacher
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
| | - Nicholas R Silvaggi
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
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Reactions of Cg10062, a cis-3-Chloroacrylic Acid Dehalogenase Homologue, with Acetylene and Allene Substrates: Evidence for a Hydration-Dependent Decarboxylation. Biochemistry 2015; 54:3009-23. [PMID: 25894805 DOI: 10.1021/acs.biochem.5b00240] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cg10062 is a cis-3-chloroacrylic acid dehalogenase (cis-CaaD) homologue from Corynebacterium glutamicum with an unknown function and an uninformative genomic context. It shares 53% pairwise sequence similarity with cis-CaaD including the six active site amino acids (Pro-1, His-28, Arg-70, Arg-73, Tyr-103, and Glu-114) that are critical for cis-CaaD activity. However, Cg10062 is a poor cis-CaaD: it lacks catalytic efficiency and isomer specificity. Two acetylene compounds (propiolate and 2-butynoate) and an allene compound, 2,3-butadienoate, were investigated as potential substrates. Cg10062 functions as a hydratase/decarboxylase using propiolate as well as the cis-3-chloro- and 3-bromoacrylates, generating mixtures of malonate semialdehyde and acetaldehyde. The two activities occur sequentially at the active site using the initial substrate. With 2,3-butadienoate and 2-butynoate, Cg10062 functions as a hydratase and converts both to acetoacetate. Mutations of the proposed water-activating residues (E114Q, E114D, and Y103F) have a range of consequences from a reduction in wild type activity to a switch of activities (i.e., hydratase into a hydratase/decarboxylase or vice versa). The intermediates for the hydration and decarboxylation products can be trapped as covalent adducts to Pro-1 when NaCNBH3 is incubated with the E114D mutant and 2,3-butadienoate or 2-butynoate, and the Y103F mutant and 2-butynoate. Three mechanisms are presented to explain these findings. One mechanism involves the direct attack of water on the substrate, whereas the other two mechanisms use covalent catalysis in which a covalent bond forms between Pro-1 and the hydration product or the substrate. The strengths and weaknesses of the mechanisms and the implications for Cg10062 function are discussed.
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48
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Singh RK, Raj I, Pujari R, Gourinath S. Crystal structures and kinetics of Type III 3-phosphoglycerate dehydrogenase reveal catalysis by lysine. FEBS J 2014; 281:5498-512. [PMID: 25294608 DOI: 10.1111/febs.13091] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 09/11/2014] [Accepted: 09/30/2014] [Indexed: 11/29/2022]
Abstract
D-Phosphoglycerate dehydrogenase (PGDH) catalyzes the first committed step of the phosphorylated serine biosynthesis pathway. Here, we report for the first time, the crystal structures of Type IIIK PGDH from Entamoeba histolytica in the apo form, as well as in complexes with substrate (3-phosphoglyceric acid) and cofactor (NAD(+) ) to 2.45, 1.8 and 2.2 Å resolution, respectively. Comparison of the apo structure with the substrate-bound structure shows that the substrate-binding domain is rotated by ~ 20° to close the active-site cleft. The cofactor-bound structure also shows a closed-cleft conformation, in which NAD(+) is bound to the nucleotide-binding domain and a formate ion occupies the substrate-binding site. Superposition of the substrate- and cofactor-bound structures represents a snapshot of the enzyme in the active form, where C2 of the substrate and C4N of the cofactor are 2.2 Å apart, and the amino group of Lys263 is close enough to the substrate to remove the proton from the hydroxyl group of PGA, indicating the role of Lys in the catalysis. Mutation of Lys263 to Ala yields just 0.8% of the specific activity of the wild-type enzyme, revealing that Lys263 indeed plays an integral role in the catalytic activity. The detectable activity of the mutant, however, indicates that after 20° rotation of the substrate-binding domain, the resulting positions of the substrate and cofactor are sufficiently close to make a productive reaction.
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Affiliation(s)
- Rohit K Singh
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
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Tuntland ML, Santarsiero BD, Johnson ME, Fung LWM. Elucidation of the bicarbonate binding site and insights into the carboxylation mechanism of (N(5))-carboxyaminoimidazole ribonucleotide synthase (PurK) from Bacillus anthracis. ACTA ACUST UNITED AC 2014; 70:3057-65. [PMID: 25372694 DOI: 10.1107/s1399004714021166] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 09/23/2014] [Indexed: 11/11/2022]
Abstract
Structures of (N(5))-carboxyaminoimidazole ribonucleotide synthase (PurK) from Bacillus anthracis with various combinations of ATP, ADP, Mg(2+), bicarbonate and aminoimidazole ribonucleotide (AIR) in the active site are presented. The binding site of bicarbonate has only been speculated upon previously, but is shown here for the first time. The binding involves interactions with the conserved residues Arg272, His274 and Lys348. These structures provide insights into each ligand in the active site and allow a possible mechanism to be proposed for the reaction that converts bicarbonate and AIR, in the presence of ATP, to produce (N(5))-carboxyaminoimidazole ribonucleotide. The formation of a carboxyphosphate intermediate through ATP phosphoryl transfer is proposed, followed by carboxylation of AIR to give the product, facilitated by a cluster of conserved residues and an active-site water network.
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Affiliation(s)
- Micheal L Tuntland
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Bernard D Santarsiero
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Michael E Johnson
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Leslie W M Fung
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
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Coenzyme A-transferase-independent butyrate re-assimilation in Clostridium acetobutylicum-evidence from a mathematical model. Appl Microbiol Biotechnol 2014; 98:9059-72. [PMID: 25149445 DOI: 10.1007/s00253-014-5987-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 07/23/2014] [Accepted: 07/24/2014] [Indexed: 01/07/2023]
Abstract
The hetero-dimeric CoA-transferase CtfA/B is believed to be crucial for the metabolic transition from acidogenesis to solventogenesis in Clostridium acetobutylicum as part of the industrial-relevant acetone-butanol-ethanol (ABE) fermentation. Here, the enzyme is assumed to mediate re-assimilation of acetate and butyrate during a pH-induced metabolic shift and to faciliate the first step of acetone formation from acetoacetyl-CoA. However, recent investigations using phosphate-limited continuous cultures have questioned this common dogma. To address the emerging experimental discrepancies, we investigated the mutant strain Cac-ctfA398s::CT using chemostat cultures. As a consequence of this mutation, the cells are unable to express functional ctfA and are thus lacking CoA-transferase activity. A mathematical model of the pH-induced metabolic shift, which was recently developed for the wild type, is used to analyse the observed behaviour of the mutant strain with a focus on re-assimilation activities for the two produced acids. Our theoretical analysis reveals that the ctfA mutant still re-assimilates butyrate, but not acetate. Based upon this finding, we conclude that C. acetobutylicum possesses a CoA-tranferase-independent butyrate uptake mechanism that is activated by decreasing pH levels. Furthermore, we observe that butanol formation is not inhibited under our experimental conditions, as suggested by previous batch culture experiments. In concordance with recent batch experiments, acetone formation is abolished in chemostat cultures using the ctfa mutant.
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