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Sendker FL, Schlotthauer T, Mais CN, Lo YK, Girbig M, Bohn S, Heimerl T, Schindler D, Weinstein A, Metzger BP, Thornton JW, Pillai A, Bange G, Schuller JM, Hochberg GK. Frequent transitions in self-assembly across the evolution of a central metabolic enzyme. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.05.602260. [PMID: 39005358 PMCID: PMC11245102 DOI: 10.1101/2024.07.05.602260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Many enzymes assemble into homomeric protein complexes comprising multiple copies of one protein. Because structural form is usually assumed to follow function in biochemistry, these assemblies are thought to evolve because they provide some functional advantage. In many cases, however, no specific advantage is known and, in some cases, quaternary structure varies among orthologs. This has led to the proposition that self-assembly may instead vary neutrally within protein families. The extent of such variation has been difficult to ascertain because quaternary structure has until recently been difficult to measure on large scales. Here, we employ mass photometry, phylogenetics, and structural biology to interrogate the evolution of homo-oligomeric assembly across the entire phylogeny of prokaryotic citrate synthases - an enzyme with a highly conserved function. We discover a menagerie of different assembly types that come and go over the course of evolution, including cases of parallel evolution and reversions from complex to simple assemblies. Functional experiments in vitro and in vivo indicate that evolutionary transitions between different assemblies do not strongly influence enzyme catalysis. Our work suggests that enzymes can wander relatively freely through a large space of possible assemblies and demonstrates the power of characterizing structure-function relationships across entire phylogenies.
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Affiliation(s)
- Franziska L. Sendker
- Max-Planck-Institute for Terrestrial Microbiology; Karl-von-Frisch-Str. 10, 35043 Marburg, Germany
| | - Tabea Schlotthauer
- Max-Planck-Institute for Terrestrial Microbiology; Karl-von-Frisch-Str. 10, 35043 Marburg, Germany
| | - Christopher-Nils Mais
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-University Marburg; Karl-von-Frisch-Str. 14, 35043 Marburg, Germany
| | - Yat Kei Lo
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-University Marburg; Karl-von-Frisch-Str. 14, 35043 Marburg, Germany
| | - Mathias Girbig
- Max-Planck-Institute for Terrestrial Microbiology; Karl-von-Frisch-Str. 10, 35043 Marburg, Germany
| | - Stefan Bohn
- Institute of Structural Biology, Helmholtz Center Munich, Ingolstädter Landstraße 1 Neuherberg, Germany
| | - Thomas Heimerl
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-University Marburg; Karl-von-Frisch-Str. 14, 35043 Marburg, Germany
| | - Daniel Schindler
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-University Marburg; Karl-von-Frisch-Str. 14, 35043 Marburg, Germany
- MaxGENESYS Biofoundry, Max-Planck-Institute for Terrestrial Microbiology; Karl-von-Frisch-Str. 10, 35043 Marburg, Germany
| | - Arielle Weinstein
- Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA
| | - Brain P. Metzger
- Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA
| | - Joseph W. Thornton
- Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
| | - Arvind Pillai
- Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA
| | - Gert Bange
- Max-Planck-Institute for Terrestrial Microbiology; Karl-von-Frisch-Str. 10, 35043 Marburg, Germany
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-University Marburg; Karl-von-Frisch-Str. 14, 35043 Marburg, Germany
- Department of Chemistry, Philipps-University Marburg; Hans-Meerwein-Str. 4, 35043 Marburg, Germany
| | - Jan M. Schuller
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-University Marburg; Karl-von-Frisch-Str. 14, 35043 Marburg, Germany
- Department of Chemistry, Philipps-University Marburg; Hans-Meerwein-Str. 4, 35043 Marburg, Germany
| | - Georg K.A. Hochberg
- Max-Planck-Institute for Terrestrial Microbiology; Karl-von-Frisch-Str. 10, 35043 Marburg, Germany
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-University Marburg; Karl-von-Frisch-Str. 14, 35043 Marburg, Germany
- Department of Chemistry, Philipps-University Marburg; Hans-Meerwein-Str. 4, 35043 Marburg, Germany
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2
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Amangeldina A, Tan ZW, Berezovsky IN. Living in trinity of extremes: Genomic and proteomic signatures of halophilic, thermophilic, and pH adaptation. Curr Res Struct Biol 2024; 7:100129. [PMID: 38327713 PMCID: PMC10847869 DOI: 10.1016/j.crstbi.2024.100129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 01/16/2024] [Accepted: 01/16/2024] [Indexed: 02/09/2024] Open
Abstract
Since nucleic acids and proteins of unicellular prokaryotes are directly exposed to extreme environmental conditions, it is possible to explore the genomic-proteomic compositional determinants of molecular mechanisms of adaptation developed by them in response to harsh environmental conditions. Using a wealth of currently available complete genomes/proteomes we were able to explore signatures of adaptation to three environmental factors, pH, salinity, and temperature, observing major trends in compositions of their nucleic acids and proteins. We derived predictors of thermostability, halophilic, and pH adaptations and complemented them by the principal components analysis. We observed a clear difference between thermophilic and salinity/pH adaptations, whereas latter invoke seemingly overlapping mechanisms. The genome-proteome compositional trade-off reveals an intricate balance between the work of base paring and base stacking in stabilization of coding DNA and r/tRNAs, and, at the same time, universal requirements for the stability and foldability of proteins regardless of the nucleotide biases. Nevertheless, we still found hidden fingerprints of ancient evolutionary connections between the nucleotide and amino acid compositions indicating their emergence, mutual evolution, and adjustment. The evolutionary perspective on the adaptation mechanisms is further studied here by means of the comparative analysis of genomic/proteomic traits of archaeal and bacterial species. The overall picture of genomic/proteomic signals of adaptation obtained here provides a foundation for future engineering and design of functional biomolecules resistant to harsh environments.
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Affiliation(s)
- Aidana Amangeldina
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, #07-01, Matrix, 138671, Singapore
- Department of Biological Sciences (DBS), National University of Singapore (NUS), 8 Medical Drive, 117579, Singapore
| | - Zhen Wah Tan
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, #07-01, Matrix, 138671, Singapore
| | - Igor N. Berezovsky
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, #07-01, Matrix, 138671, Singapore
- Department of Biological Sciences (DBS), National University of Singapore (NUS), 8 Medical Drive, 117579, Singapore
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3
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Pathirage R, Favrot L, Petit C, Yamsek M, Singh S, Mallareddy JR, Rana S, Natarajan A, Ronning DR. Mycobacterium tuberculosis CitA activity is modulated by cysteine oxidation and pyruvate binding. RSC Med Chem 2023; 14:921-933. [PMID: 37252106 PMCID: PMC10211323 DOI: 10.1039/d3md00058c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Accepted: 04/05/2023] [Indexed: 11/12/2023] Open
Abstract
As an adaptation for survival during infection, Mycobacterium tuberculosis becomes dormant, reducing its metabolism and growth. Two types of citrate synthases have been identified in Mycobacterium tuberculosis, GltA2 and CitA. Previous work shows that overexpression of CitA, the secondary citrate synthase, stimulates the growth of Mycobacterium tuberculosis under hypoxic conditions without showing accumulation of triacylglycerols and makes mycobacteria more sensitive to antibiotics, suggesting that CitA may play a role as a metabolic switch during infection and may be an interesting TB drug target. To assess the druggability and possible mechanisms of targeting CitA with small-molecule compounds, the CitA crystal structure was solved to 2.1 Å by X-ray crystallography. The solved structure shows that CitA lacks an NADH binding site that would afford allosteric regulation, which is atypical of most citrate synthases. However, a pyruvate molecule is observed within the analogous domain, suggesting pyruvate may instead be the allosteric regulator for CitA. The R149 and R153 residues forming the charged portion of the pyruvate binding pocket were mutated to glutamate and methionine, respectively, to assess the effect of mutations on activity. Protein thermal shift assay shows thermal stabilization of CitA in the presence of pyruvate compared to the two CitA variants designed to decrease pyruvate affinity. Solved crystal structures of both variants show no significant structural changes. However, the catalytic efficiency of the R153M variant increases by 2.6-fold. Additionally, we show that covalent modification of C143 of CitA by Ebselen completely arrests enzyme activity. Similar inhibition is observed using two spirocyclic Michael acceptor containing compounds, which inhibit CitA with ICapp50 values of 6.6 and 10.9 μM. A crystal structure of CitA modified by Ebselen was solved, but significant structural changes were lacking. Considering that covalent modification of C143 inactivates CitA and the proximity of C143 to the pyruvate binding site, this suggests that structural and/or chemical changes in this sub-domain are responsible for regulating CitA enzymatic activity.
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Affiliation(s)
- Rasangi Pathirage
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center Omaha NE 68198 USA
| | - Lorenza Favrot
- Department of Chemistry and Biochemistry, University of Toledo Toledo OH 43606 USA
| | - Cecile Petit
- Department of Chemistry and Biochemistry, University of Toledo Toledo OH 43606 USA
| | - Melvin Yamsek
- Department of Chemistry and Biochemistry, University of Toledo Toledo OH 43606 USA
| | - Sarbjit Singh
- Eppley Institute for Cancer Research, University of Nebraska Medical Center Omaha NE 68198 USA
| | | | - Sandeep Rana
- Eppley Institute for Cancer Research, University of Nebraska Medical Center Omaha NE 68198 USA
| | - Amarnath Natarajan
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center Omaha NE 68198 USA
- Eppley Institute for Cancer Research, University of Nebraska Medical Center Omaha NE 68198 USA
- Department of Genetics Cell Biology and Anatomy, University of Nebraska Medical Center Omaha NE 68198 USA
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center Omaha NE USA
| | - Donald R Ronning
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center Omaha NE 68198 USA
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Williams K, Szwalbe AJ, de Mattos-Shipley KMJ, Bailey AM, Cox RJ, Willis CL. Maleidride biosynthesis - construction of dimeric anhydrides - more than just heads or tails. Nat Prod Rep 2023; 40:128-157. [PMID: 36129067 PMCID: PMC9890510 DOI: 10.1039/d2np00041e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Covering: up to early 2022Maleidrides are a family of polyketide-based dimeric natural products isolated from fungi. Many maleidrides possess significant bioactivities, making them attractive pharmaceutical or agrochemical lead compounds. Their unusual biosynthetic pathways have fascinated scientists for decades, with recent advances in our bioinformatic and enzymatic understanding providing further insights into their construction. However, many intriguing questions remain, including exactly how the enzymatic dimerisation, which creates the diverse core structure of the maleidrides, is controlled. This review will explore the literature from the initial isolation of maleidride compounds in the 1930s, through the first full structural elucidation in the 1960s, to the most recent in vivo, in vitro, and in silico analyses.
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Affiliation(s)
- Katherine Williams
- School of Biological Sciences, Life Sciences Building, University of Bristol, 24 Tyndall Ave, Bristol BS8 1TQ, UK.
| | | | | | - Andy M. Bailey
- School of Biological Sciences, Life Sciences Building, University of Bristol24 Tyndall AveBristol BS8 1TQUK
| | - Russell J. Cox
- Institute for Organic Chemistry and BMWZ, Leibniz University of HannoverSchneiderberg 3830167HannoverGermany
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Leucine-Responsive Regulatory Protein in Acetic Acid Bacteria Is Stable and Functions at a Wide Range of Intracellular pH Levels. J Bacteriol 2021; 203:e0016221. [PMID: 34228496 DOI: 10.1128/jb.00162-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acetic acid bacteria grow while producing acetic acid, resulting in acidification of the culture. Limited reports elucidate the effect of changes in intracellular pH on transcriptional factors. In the present study, the intracellular pH of Komagataeibacter europaeus was monitored with a pH-sensitive green fluorescent protein, showing that the intracellular pH decreased from 6.3 to 4.7 accompanied by acetic acid production during cell growth. The leucine-responsive regulatory protein of K. europaeus (KeLrp) was used as a model to examine pH-dependent effects, and its properties were compared with those of the Escherichia coli ortholog (EcLrp) at different pH levels. The DNA-binding activities of EcLrp and KeLrp with the target DNA (Ec-ilvI and Ke-ilvI) were examined by gel mobility shift assays under various pH conditions. EcLrp showed the highest affinity with the target at pH 8.0 (Kd [dissociation constant], 0.7 μM), decreasing to a minimum of 3.4 μM at pH 4.0. Conversely, KeLrp did not show significant differences in binding affinity between pH 4 and 7 (Kd, 1.0 to 1.5 μM), and the highest affinity was at pH 5.0 (Kd, 1.0 μM). Circular dichroism spectroscopy revealed that the α-helical content of KeLrp was the highest at pH 5.0 (49%) and was almost unchanged while being maintained at >45% over a range of pH levels examined, while that of EcLrp decreased from its maximum (49% at pH 7.0) to its minimum (36% at pH 4.0). These data indicate that KeLrp is stable and functions over a wide range of intracellular pH levels. IMPORTANCE Lrp is a highly conserved transcriptional regulator found in bacteria and archaea and regulates transcriptions of various genes. The intracellular pH of acetic acid bacteria (AAB) changes accompanied by acetic acid production during cell growth. The Lrp of AAB K. europaeus (KeLrp) was structurally stable over a wide range of pH and maintained DNA-binding activity even at low pH compared with Lrp from E. coli living in a neutral environment. An in vitro experiment showed DNA-binding activity of KeLrp to the target varied with changes in pH. In AAB, change of the intracellular pH during a cell growth would be an important trigger in controlling the activity of Lrp in vivo.
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Park SH, Lee CW, Bae DW, Do H, Jeong CS, Hwang J, Cha SS, Lee JH. Structural basis of the cooperative activation of type II citrate synthase (HyCS) from Hymenobacter sp. PAMC 26554. Int J Biol Macromol 2021; 183:213-221. [PMID: 33910038 DOI: 10.1016/j.ijbiomac.2021.04.141] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 04/20/2021] [Accepted: 04/22/2021] [Indexed: 12/01/2022]
Abstract
Citrate synthase (CS) catalyzes the formation of citrate and coenzyme A from acetyl-CoA and oxaloacetate. CS exists in two forms: type I and type II. We determined the citrate-bound crystal structure of type II CS from the Hymenobacter sp. PAMC 26554 bacterium (HyCS; isolated from Antarctic lichen). Citrate molecules bound to a cleft between the large and small domains of HyCS. Structural comparison of HyCS with other type II CSs revealed that type II CSs have a highly conserved flexible hinge region (residues G264-P265 in HyCS), enabling correct positioning of active site residues. Notably, the catalytic His266 residue of HyCS interacted with Trp262 in the inactive (unliganded open) state of other type II CSs, whereas the His266 residue moved to the active site via a small-domain swing motion, interacting with the bound citrate in the closed conformation of HyCS. However, type I CSs lack this tryptophan residue and face-to-edge interactions. Thus, type II CSs might have a unique domain-motion control mechanism enabling a tight allosteric regulation. An activity assay using a W262A mutant showed a Hill coefficient of 2.4; thus, the interaction between Trp262 and His266 was closely related to the positive cooperative ligand binding of type II CS.
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Affiliation(s)
- Sun-Ha Park
- Research Unit of Cryogenic Novel Material, Korea Polar Research Institute, Incheon 21990, Republic of Korea
| | - Chang Woo Lee
- Research Unit of Cryogenic Novel Material, Korea Polar Research Institute, Incheon 21990, Republic of Korea; Department of Polar Sciences, University of Science and Technology, Incheon 21990, Republic of Korea
| | - Da-Woon Bae
- Department of Chemistry & Nanoscience, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Hackwon Do
- Research Unit of Cryogenic Novel Material, Korea Polar Research Institute, Incheon 21990, Republic of Korea
| | - Chang-Sook Jeong
- Research Unit of Cryogenic Novel Material, Korea Polar Research Institute, Incheon 21990, Republic of Korea; Department of Polar Sciences, University of Science and Technology, Incheon 21990, Republic of Korea
| | - Jisub Hwang
- Research Unit of Cryogenic Novel Material, Korea Polar Research Institute, Incheon 21990, Republic of Korea; Department of Polar Sciences, University of Science and Technology, Incheon 21990, Republic of Korea
| | - Sun-Shin Cha
- Department of Chemistry & Nanoscience, Ewha Womans University, Seoul 03760, Republic of Korea.
| | - Jun Hyuck Lee
- Research Unit of Cryogenic Novel Material, Korea Polar Research Institute, Incheon 21990, Republic of Korea; Department of Polar Sciences, University of Science and Technology, Incheon 21990, Republic of Korea.
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7
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Yin S, Friedrich S, Hrupins V, Cox RJ. In vitro studies of maleidride-forming enzymes. RSC Adv 2021; 11:14922-14931. [PMID: 35424071 PMCID: PMC8697804 DOI: 10.1039/d1ra02118d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 04/15/2021] [Indexed: 11/21/2022] Open
Abstract
In vitro assays of enzymes involved in the biosynthesis of maleidrides from polyketides in fungi were performed. The results show that the enzymes are closely related to primary metabolism enzymes of the citric acid cycle in terms of stereochemical preferences, but with an expanded substrate selectivity. A key citrate synthase can react both saturated and unsaturated acyl CoA substrates to give solely anti substituted citrates. This undergoes anti-dehydration to afford an unsaturated precursor which is cyclised in vitro by ketosteroid-isomerase-like enzymes to give byssochlamic acid.
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Affiliation(s)
- Sen Yin
- OCI, BMWZ, Leibniz University of Hannover Schneiderberg 38 30167 Hannover Germany
| | - Steffen Friedrich
- OCI, BMWZ, Leibniz University of Hannover Schneiderberg 38 30167 Hannover Germany
| | - Vjaceslavs Hrupins
- OCI, BMWZ, Leibniz University of Hannover Schneiderberg 38 30167 Hannover Germany
| | - Russell J Cox
- OCI, BMWZ, Leibniz University of Hannover Schneiderberg 38 30167 Hannover Germany
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Qiu X, Zhang Y, Hong H. Classification of acetic acid bacteria and their acid resistant mechanism. AMB Express 2021; 11:29. [PMID: 33595734 PMCID: PMC7889782 DOI: 10.1186/s13568-021-01189-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 02/04/2021] [Indexed: 12/14/2022] Open
Abstract
Acetic acid bacteria (AAB) are obligate aerobic Gram-negative bacteria that are commonly used in vinegar fermentation because of their strong capacity for ethanol oxidation and acetic acid synthesis as well as their acid resistance. However, low biomass and low production rate due to acid stress are still major challenges that must be overcome in industrial processes. Although acid resistance in AAB is important to the production of high acidity vinegar, the acid resistance mechanisms of AAB have yet to be fully elucidated. In this study, we discuss the classification of AAB species and their metabolic processes and review potential acid resistance factors and acid resistance mechanisms in various strains. In addition, we analyze the quorum sensing systems of Komagataeibacter and Gluconacetobacter to provide new ideas for investigation of acid resistance mechanisms in AAB in the form of signaling pathways. The results presented herein will serve as an important reference for selective breeding of high acid resistance AAB and optimization of acetic acid fermentation processes.
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Affiliation(s)
- Xiaoman Qiu
- College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, No. 30, Puzhu Road, Nanjing, 211800, China
- National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, No. 30, Puzhu Road, Nanjing, 211800, China
| | - Yao Zhang
- College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, No. 30, Puzhu Road, Nanjing, 211800, China
- National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, No. 30, Puzhu Road, Nanjing, 211800, China
| | - Housheng Hong
- College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, No. 30, Puzhu Road, Nanjing, 211800, China.
- National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, No. 30, Puzhu Road, Nanjing, 211800, China.
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9
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Nguyen VH, Singh N, Medina A, Usón I, Fraser ME. Identification of the active site residues in ATP-citrate lyase's carboxy-terminal portion. Protein Sci 2019; 28:1840-1849. [PMID: 31411782 DOI: 10.1002/pro.3708] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Revised: 08/08/2019] [Accepted: 08/12/2019] [Indexed: 01/25/2023]
Abstract
ATP-citrate lyase (ACLY) catalyzes production of acetyl-CoA and oxaloacetate from CoA and citrate using ATP. In humans, this cytoplasmic enzyme connects energy metabolism from carbohydrates to the production of lipids. In certain bacteria, ACLY is used to fix carbon in the reductive tricarboxylic acid cycle. The carboxy(C)-terminal portion of ACLY shows sequence similarity to citrate synthase of the tricarboxylic acid cycle. To investigate the roles of residues of ACLY equivalent to active site residues of citrate synthase, these residues in ACLY from Chlorobium limicola were mutated, and the proteins were investigated using kinetics assays and biophysical techniques. To obtain the crystal structure of the C-terminal portion of ACLY, full-length C. limicola ACLY was cleaved, first non-specifically with chymotrypsin and subsequently with Tobacco Etch Virus protease. Crystals of the C-terminal portion diffracted to high resolution, providing structures that show the positions of active site residues and how ACLY tetramerizes.
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Affiliation(s)
- Vinh H Nguyen
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Noreen Singh
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Ana Medina
- Structural Biology Unit, CSIC, Barcelona, Spain
| | - Isabel Usón
- Structural Biology Unit, CSIC, Barcelona, Spain.,ICREA, Barcelona, Spain
| | - Marie E Fraser
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
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10
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Ito S, Koyama N, Osanai T. Citrate synthase from Synechocystis is a distinct class of bacterial citrate synthase. Sci Rep 2019; 9:6038. [PMID: 30988396 PMCID: PMC6465352 DOI: 10.1038/s41598-019-42659-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 04/04/2019] [Indexed: 12/03/2022] Open
Abstract
Citrate synthase (CS, EC 2.3.3.1) catalyses the initial reaction of the tricarboxylic acid (TCA) cycle. Although CSs from heterotrophic bacteria have been extensively studied, cyanobacterial CSs are not well-understood. Cyanobacteria can produce various metabolites from carbon dioxide. Synechocystis sp. PCC 6803 (Synechocystis 6803) is a cyanobacterium used to synthesize metabolites through metabolic engineering techniques. The production of acetyl-CoA-derived metabolites in Synechocystis 6803 has been widely examined. However, the biochemical mechanisms of reactions involving acetyl-CoA in Synechocystis 6803 are poorly understood. We characterised the CS from Synechocystis 6803 (SyCS) and compared its characteristics with other bacterial CSs. SyCS catalysed only the generation of citrate, and did not catalyse the cleavage of citrate. It is suggested that SyCS is not related to the reductive TCA cycle. The substrate affinity and turnover number of SyCS were lower than those of CSs from heterotrophic bacteria. SyCS was activated by MgCl2 and CaCl2, which inhibit various bacterial CSs. SyCS was not inhibited by ATP and NADH; which are typical feedback inhibitors of other bacterial CSs. SyCS was inhibited by phosphoenolpyruvate and activated by ADP, which has not been reported for CSs from heterotrophic bacteria. Thus, SyCS showed unique characteristics, particularly its sensitivity to effectors.
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Affiliation(s)
- Shoki Ito
- School of Agriculture, Meiji University, 1-1-1, Higashimita, Tama-ku, Kawasaki, Kanagawa, 214-8571, Japan
| | - Naoto Koyama
- School of Agriculture, Meiji University, 1-1-1, Higashimita, Tama-ku, Kawasaki, Kanagawa, 214-8571, Japan
| | - Takashi Osanai
- School of Agriculture, Meiji University, 1-1-1, Higashimita, Tama-ku, Kawasaki, Kanagawa, 214-8571, Japan.
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11
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Venkat S, Chen H, McGuire P, Stahman A, Gan Q, Fan C. Characterizing lysine acetylation of Escherichia coli type II citrate synthase. FEBS J 2019; 286:2799-2808. [PMID: 30974512 DOI: 10.1111/febs.14845] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 03/19/2019] [Accepted: 04/09/2019] [Indexed: 11/27/2022]
Abstract
The citrate synthase (CS) catalyzes the first reaction of the tricarboxylic acid cycle, playing an important role in central metabolism. The acetylation of lysine residues in the Escherichia coli Type II CS has been identified at multiple sites by proteomic studies, but their effects remain unknown. In this study, we applied the genetic code expansion strategy to generate 10 site-specifically acetylated CS variants which have been identified in nature. Enzyme assays and kinetic analyses showed that lysine acetylation could decrease the overall CS enzyme activity, largely due to the acetylation of K295 which impaired the binding of acetyl-coenzyme A. Further genetic studies as well as in vitro acetylation and deacetylation assays were performed to explore the acetylation and deacetylation processes of the CS, which indicated that the CS could be acetylated by acetyl-phosphate chemically, and be deacetylated by the CobB deacetylase.
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Affiliation(s)
- Sumana Venkat
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, USA
| | - Hao Chen
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, USA
| | - Paige McGuire
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | - Alleigh Stahman
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR, USA
| | - Qinglei Gan
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR, USA
| | - Chenguang Fan
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, USA.,Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR, USA
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12
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An allosteric mechanism for potent inhibition of human ATP-citrate lyase. Nature 2019; 568:566-570. [PMID: 30944472 DOI: 10.1038/s41586-019-1094-6] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Accepted: 03/08/2019] [Indexed: 11/08/2022]
Abstract
ATP-citrate lyase (ACLY) is a central metabolic enzyme and catalyses the ATP-dependent conversion of citrate and coenzyme A (CoA) to oxaloacetate and acetyl-CoA1-5. The acetyl-CoA product is crucial for the metabolism of fatty acids6,7, the biosynthesis of cholesterol8, and the acetylation and prenylation of proteins9,10. There has been considerable interest in ACLY as a target for anti-cancer drugs, because many cancer cells depend on its activity for proliferation2,5,11. ACLY is also a target against dyslipidaemia and hepatic steatosis, with a compound currently in phase 3 clinical trials4,5. Many inhibitors of ACLY have been reported, but most of them have weak activity5. Here we report the development of a series of low nanomolar, small-molecule inhibitors of human ACLY. We have also determined the structure of the full-length human ACLY homo-tetramer in complex with one of these inhibitors (NDI-091143) by cryo-electron microscopy, which reveals an unexpected mechanism of inhibition. The compound is located in an allosteric, mostly hydrophobic cavity next to the citrate-binding site, and requires extensive conformational changes in the enzyme that indirectly disrupt citrate binding. The observed binding mode is supported by and explains the structure-activity relationships of these compounds. This allosteric site greatly enhances the 'druggability' of ACLY and represents an attractive target for the development of new ACLY inhibitors.
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Lee SH, Son HF, Kim KJ. Structural insights into the inhibition properties of archaeon citrate synthase from Metallosphaera sedula. PLoS One 2019; 14:e0212807. [PMID: 30794680 PMCID: PMC6386500 DOI: 10.1371/journal.pone.0212807] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 02/08/2019] [Indexed: 11/19/2022] Open
Abstract
Metallosphaera sedula is a thermoacidophilic archaeon and has an incomplete TCA/glyoxylate cycle that is used for production of biosynthetic precursors of essential metabolites. Citrate synthase from M. sedula (MsCS) is an enzyme involved in the first step of the incomplete TCA/glyoxylate cycle by converting oxaloacetate and acetyl-CoA into citrate and coenzyme A. To elucidate the inhibition properties of MsCS, we determined its crystal structure at 1.7 Å resolution. Like other Type-I CS, MsCS functions as a dimer and each monomer consists of two distinct domains, a large domain and a small domain. The oxaloacetate binding site locates at the cleft between the two domains, and the active site was more closed upon binding of the oxaloacetate substrate than binding of the citrate product. Interestingly, the inhibition kinetic analysis showed that, unlike other Type-I CSs, MsCS is non-competitively inhibited by NADH. Finally, amino acids and structural comparison of MsCS with other Type-II CSs, which were reported to be non-competitively inhibited by NADH, revealed that MsCS has quite unique NADH binding mode for non-competitive inhibition.
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Affiliation(s)
- Seul Hoo Lee
- School of Life Sciences (KNU Creative BioResearch Group), KNU Institute for Microorganisms, Kyungpook National University, Daegu, Republic of Korea
| | - Hyeoncheol Francis Son
- School of Life Sciences (KNU Creative BioResearch Group), KNU Institute for Microorganisms, Kyungpook National University, Daegu, Republic of Korea
| | - Kyung-Jin Kim
- School of Life Sciences (KNU Creative BioResearch Group), KNU Institute for Microorganisms, Kyungpook National University, Daegu, Republic of Korea
- * E-mail:
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14
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Xu M, Singla J, Tocheva EI, Chang YW, Stevens RC, Jensen GJ, Alber F. De Novo Structural Pattern Mining in Cellular Electron Cryotomograms. Structure 2019; 27:679-691.e14. [PMID: 30744995 DOI: 10.1016/j.str.2019.01.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 07/27/2018] [Accepted: 01/14/2019] [Indexed: 11/16/2022]
Abstract
Electron cryotomography enables 3D visualization of cells in a near-native state at molecular resolution. The produced cellular tomograms contain detailed information about a plethora of macromolecular complexes, their structures, abundances, and specific spatial locations in the cell. However, extracting this information in a systematic way is very challenging, and current methods usually rely on individual templates of known structures. Here, we propose a framework called "Multi-Pattern Pursuit" for de novo discovery of different complexes from highly heterogeneous sets of particles extracted from entire cellular tomograms without using information of known structures. These initially detected structures can then serve as input for more targeted refinement efforts. Our tests on simulated and experimental tomograms show that our automated method is a promising tool for supporting large-scale template-free visual proteomics analysis.
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Affiliation(s)
- Min Xu
- Computational Biology Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Jitin Singla
- Institute for Quantitative and Computational Biosciences, Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095, USA; Quantitative and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Elitza I Tocheva
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Yi-Wei Chang
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Raymond C Stevens
- Department of Biological Sciences and Department of Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Grant J Jensen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA; Howard Hughes Medical Institute, Pasadena, CA 91125, USA
| | - Frank Alber
- Institute for Quantitative and Computational Biosciences, Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095, USA; Quantitative and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA.
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15
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Effects of gltA and arcA Mutations on Biomass and 1,3-Propanediol Production in Klebsiella pneumoniae. BIOTECHNOL BIOPROC E 2019. [DOI: 10.1007/s12257-018-0246-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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16
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Lee SH, Kim KJ. Crystal structure and biochemical properties of msed_0281, the citrate synthase from Metallosphaera sedula. Biochem Biophys Res Commun 2019; 509:722-727. [PMID: 30611567 DOI: 10.1016/j.bbrc.2018.12.172] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Accepted: 12/27/2018] [Indexed: 11/25/2022]
Abstract
Metallosphaera sedula is a thermoacidophilic archaeon that has carbon fixation ability using the 3-hydroxypropionate/4-hydroxybutyrate(3-HP/4-HB) cycle, and has an incomplete TCA cycle to produce necessary biosynthetic precursors. The citrate synthase from M. sedula (MsCS) is an enzyme involved in the first step of the incomplete TCA cycle, catalyzing the conversion of oxaloacetate and acetyl-CoA into citrate and coenzyme A. To investigate the molecular mechanism of MsCS, we determined its crystal structure at 1.8 Å resolution. As other known CSs, MsCS functions as a dimer, and each monomer consists of two domains, a large domain and a small domain. We also determined the structure of the complex with acetyl-CoA and revealed the acetyl-CoA binding mode of MsCS. Structural comparison of MsCS with another CS in complex with oxaloacetate enabled us to predict the oxaloacetate binding site. Moreover, we performed inhibitory kinetic analyses of MsCS, and showed that the protein is inhibited by citrate and ATP by competitive and non-competitive inhibition modes, respectively, but not by NADH. Based on these results, we suggest that MsCS belongs to the type-I CS with structural and biochemical properties similar to those of CSs involved in the conventional TCA cycle.
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Affiliation(s)
- Seul Hoo Lee
- School of Life Sciences (KNU Creative BioResearch Group), KNU Institute for Microorganisms, Kyungpook National University, Daegu, 41566, Republic of Korea
| | - Kyung-Jin Kim
- School of Life Sciences (KNU Creative BioResearch Group), KNU Institute for Microorganisms, Kyungpook National University, Daegu, 41566, Republic of Korea.
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17
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Kittilä T, Cryle MJ. An enhanced chemoenzymatic method for loading substrates onto carrier protein domains. Biochem Cell Biol 2017; 96:372-379. [PMID: 29172027 DOI: 10.1139/bcb-2017-0275] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Non-ribosomal peptide synthetase (NRPS) machineries produce many medically relevant peptides that cannot be easily accessed by chemical synthesis. Thus, understanding NRPS mechanism is of crucial importance to allow efficient redesign of these machineries to produce new compounds. During NRPS-mediated synthesis, substrates are covalently attached to peptidyl carrier proteins (PCPs), and studies of NRPSs are impeded by difficulties in producing PCPs loaded with substrates. Different approaches to load substrates onto PCP domains have been described, but all suffer from difficulties in either the complexity of chemical synthesis or low enzymatic efficiency. Here, we describe an enhanced chemoenzymatic loading method that combines 2 approaches into a single, highly efficient one-pot loading reaction. First, d-pantetheine and ATP are converted into dephospho-coenzyme A via the actions of 2 enzymes from coenzyme A (CoA) biosynthesis. Next, phosphoadenylates are dephosphorylated using alkaline phosphatase to allow linker attachment to PCP domain by Sfp mutant R4-4, which is inhibited by phosphoadenylates. This route does not depend on activity of the commonly problematic dephospho-CoA kinase and, therefore, offers an improved method for substrate loading onto PCP domains.
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Affiliation(s)
- Tiia Kittilä
- a Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany
| | - Max J Cryle
- a Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.,b The Monash Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.,c EMBL Australia, Monash University, Clayton, Victoria 3800, Australia
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18
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Teoh WK, Salleh FM, Shahir S. Characterization of Thiomonas delicata arsenite oxidase expressed in Escherichia coli. 3 Biotech 2017; 7:97. [PMID: 28560637 DOI: 10.1007/s13205-017-0740-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 01/20/2017] [Indexed: 11/26/2022] Open
Abstract
Microbial arsenite oxidation is an essential biogeochemical process whereby more toxic arsenite is oxidized to the less toxic arsenate. Thiomonas strains represent an important arsenite oxidizer found ubiquitous in acid mine drainage. In the present study, the arsenite oxidase gene (aioBA) was cloned from Thiomonas delicata DSM 16361, expressed heterologously in E. coli and purified to homogeneity. The purified recombinant Aio consisted of two subunits with the respective molecular weights of 91 and 21 kDa according to SDS-PAGE. Aio catalysis was optimum at pH 5.5 and 50-55 °C. Aio exhibited stability under acidic conditions (pH 2.5-6). The V max and K m values of the enzyme were found to be 4 µmol min-1 mg-1 and 14.2 µM, respectively. SDS and Triton X-100 were found to inhibit the enzyme activity. The homology model of Aio showed correlation with the acidophilic adaptation of the enzyme. This is the first characterization studies of Aio from a species belonging to the Thiomonas genus. The arsenite oxidase was found to be among the acid-tolerant Aio reported to date and has the potential to be used for biosensor and bioremediation applications in acidic environments.
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Affiliation(s)
- Wei Kheng Teoh
- Department of Biosciences and Health Sciences, Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310, Skudai, Johor, Malaysia
| | - Faezah Mohd Salleh
- Department of Biosciences and Health Sciences, Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310, Skudai, Johor, Malaysia
| | - Shafinaz Shahir
- Department of Biosciences and Health Sciences, Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310, Skudai, Johor, Malaysia.
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19
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Murphy JR, Mullins EA, Kappock TJ. Functional Dissection of the Bipartite Active Site of the Class I Coenzyme A (CoA)-Transferase Succinyl-CoA:Acetate CoA-Transferase. Front Chem 2016; 4:23. [PMID: 27242998 PMCID: PMC4876117 DOI: 10.3389/fchem.2016.00023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Accepted: 04/28/2016] [Indexed: 12/04/2022] Open
Abstract
Coenzyme A (CoA)-transferases catalyze the reversible transfer of CoA from acyl-CoA thioesters to free carboxylates. Class I CoA-transferases produce acylglutamyl anhydride intermediates that undergo attack by CoA thiolate on either the internal or external carbonyl carbon atoms, forming distinct tetrahedral intermediates <3 Å apart. In this study, crystal structures of succinyl-CoA:acetate CoA-transferase (AarC) from Acetobacter aceti are used to examine how the Asn347 carboxamide stabilizes the internal oxyanion intermediate. A structure of the active mutant AarC-N347A bound to CoA revealed both solvent replacement of the missing contact and displacement of the adjacent Glu294, indicating that Asn347 both polarizes and orients the essential glutamate. AarC was crystallized with the nonhydrolyzable acetyl-CoA (AcCoA) analog dethiaacetyl-CoA (1a) in an attempt to trap a closed enzyme complex containing a stable analog of the external oxyanion intermediate. One active site contained an acetylglutamyl anhydride adduct and truncated 1a, an unexpected result hinting at an unprecedented cleavage of the ketone moiety in 1a. Solution studies confirmed that 1a decomposition is accompanied by production of near-stoichiometric acetate, in a process that seems to depend on microbial contamination but not AarC. A crystal structure of AarC bound to the postulated 1a truncation product (2a) showed complete closure of one active site per dimer but no acetylglutamyl anhydride, even with acetate added. These findings suggest that an activated acetyl donor forms during 1a decomposition; a working hypothesis involving ketone oxidation is offered. The ability of 2a to induce full active site closure furthermore suggests that it subverts a system used to impede inappropriate active site closure on unacylated CoA.
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Affiliation(s)
- Jesse R Murphy
- Department of Biochemistry, Purdue University West Lafayette, IN, USA
| | - Elwood A Mullins
- Department of Biochemistry, Purdue University West Lafayette, IN, USA
| | - T Joseph Kappock
- Department of Biochemistry, Purdue University West Lafayette, IN, USA
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20
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Murphy JR, Donini S, Kappock TJ. An active site-tail interaction in the structure of hexahistidine-tagged Thermoplasma acidophilum citrate synthase. Acta Crystallogr F Struct Biol Commun 2015; 71:1292-9. [PMID: 26457521 PMCID: PMC4601594 DOI: 10.1107/s2053230x15015939] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 08/25/2015] [Indexed: 11/29/2022] Open
Abstract
Citrate synthase (CS) plays a central metabolic role in aerobes and many other organisms. The CS reaction comprises two half-reactions: a Claisen aldol condensation of acetyl-CoA (AcCoA) and oxaloacetate (OAA) that forms citryl-CoA (CitCoA), and CitCoA hydrolysis. Protein conformational changes that `close' the active site play an important role in the assembly of a catalytically competent condensation active site. CS from the thermoacidophile Thermoplasma acidophilum (TpCS) possesses an endogenous Trp fluorophore that can be used to monitor the condensation reaction. The 2.2 Å resolution crystal structure of TpCS fused to a C-terminal hexahistidine tag (TpCSH6) reported here is an `open' structure that, when compared with several liganded TpCS structures, helps to define a complete path for active-site closure. One active site in each dimer binds a neighboring His tag, the first nonsubstrate ligand known to occupy both the AcCoA and OAA binding sites. Solution data collectively suggest that this fortuitous interaction is stabilized by the crystalline lattice. As a polar but almost neutral ligand, the active site-tail interaction provides a new starting point for the design of bisubstrate-analog inhibitors of CS.
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Affiliation(s)
- Jesse R. Murphy
- Department of Biochemistry, Purdue University, 175 South University Street, West Lafayette, IN 47907-2063, USA
| | - Stefano Donini
- Department of Biochemistry, Purdue University, 175 South University Street, West Lafayette, IN 47907-2063, USA
| | - T. Joseph Kappock
- Department of Biochemistry, Purdue University, 175 South University Street, West Lafayette, IN 47907-2063, USA
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21
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Adaptation and tolerance of bacteria against acetic acid. Appl Microbiol Biotechnol 2015; 99:6215-29. [DOI: 10.1007/s00253-015-6762-3] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Revised: 06/05/2015] [Accepted: 06/15/2015] [Indexed: 10/23/2022]
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22
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Liu Y, Tang H, Lin Z, Xu P. Mechanisms of acid tolerance in bacteria and prospects in biotechnology and bioremediation. Biotechnol Adv 2015; 33:1484-92. [PMID: 26057689 DOI: 10.1016/j.biotechadv.2015.06.001] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 06/02/2015] [Accepted: 06/02/2015] [Indexed: 02/05/2023]
Abstract
Acidogenic and aciduric bacteria have developed several survival systems in various acidic environments to prevent cell damage due to acid stress such as that on the human gastric surface and in the fermentation medium used for industrial production of acidic products. Common mechanisms for acid resistance in bacteria are proton pumping by F1-F0-ATPase, the glutamate decarboxylase system, formation of a protective cloud of ammonia, high cytoplasmic urease activity, repair or protection of macromolecules, and biofilm formation. The field of synthetic biology has rapidly advanced and generated an ever-increasing assortment of genetic devices and biological modules for applications in biofuel and novel biomaterial productions. Better understanding of aspects such as overproduction of general shock proteins, molecular mechanisms, and responses to cell density adopted by microorganisms for survival in low pH conditions will prove useful in synthetic biology for potential industrial and environmental applications.
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Affiliation(s)
- Yuping Liu
- State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China; School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Hongzhi Tang
- State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China; School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
| | - Zhanglin Lin
- Department of Chemical Engineering, Tsinghua University, One Tsinghua Garden Road, Beijing 100084, People's Republic of China
| | - Ping Xu
- State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China; School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
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23
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Kobylarz MJ, Grigg JC, Sheldon JR, Heinrichs DE, Murphy MEP. SbnG, a citrate synthase in Staphylococcus aureus: a new fold on an old enzyme. J Biol Chem 2014; 289:33797-807. [PMID: 25336653 DOI: 10.1074/jbc.m114.603175] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In response to iron deprivation, Staphylococcus aureus produces staphyloferrin B, a citrate-containing siderophore that delivers iron back to the cell. This bacterium also possesses a second citrate synthase, SbnG, that is necessary for supplying citrate to the staphyloferrin B biosynthetic pathway. We present the structure of SbnG bound to the inhibitor calcium and an active site variant in complex with oxaloacetate. The overall fold of SbnG is structurally distinct from TCA cycle citrate synthases yet similar to metal-dependent class II aldolases. Phylogenetic analyses revealed that SbnG forms a separate clade with homologs from other siderophore biosynthetic gene clusters and is representative of a metal-independent subgroup in the phosphoenolpyruvate/pyruvate domain superfamily. A structural superposition of the SbnG active site to TCA cycle citrate synthases and site-directed mutagenesis suggests a case for convergent evolution toward a conserved catalytic mechanism for citrate production.
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Affiliation(s)
- Marek J Kobylarz
- From the Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada and
| | - Jason C Grigg
- From the Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada and
| | | | - David E Heinrichs
- the Department of Microbiology and Immunology and the Centre for Human Immunology University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Michael E P Murphy
- From the Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada and
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24
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Liao CH, Yao LL, Ye BC. Three genes encoding citrate synthases in Saccharopolyspora erythraea are regulated by the global nutrient-sensing regulators GlnR, DasR, and CRP. Mol Microbiol 2014; 94:1065-1084. [PMID: 25294017 DOI: 10.1111/mmi.12818] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2014] [Indexed: 02/06/2023]
Abstract
Saccharopolyspora erythraea has three citrate synthases encoded by gltA-2, citA, and citA4. Here, we characterized and identified the expression and regulatory properties of these synthases. Three pleiotropic global regulatory proteins of S. erythraea - CRP, GlnR, and DasR - are involved in carbon metabolism, nitrogen metabolism, and amino-sugar (chitin and GlcNAc) metabolism. Using electrophoretic mobility shift assays (EMSAs), we identified these regulators as proteins that bind directly to the promoter regions of all citrate synthase genes (gltA-2, citA, and citA4). Footprinting assays indicated the exact protect sequences of CRP, GlnR, and DasR on the promoter region of gltA-2, revealing binding competition between GlnR and DasR. Moreover, by comparing the transcription levels of citrate synthase genes between parental and glnR mutant or dasR mutant strains, or by comparing the transcription response of citrate synthases under various nutrient conditions, we found that GlnR and DasR negatively regulated citA and citA4 transcription but had no regulatory effects on the gltA-2 gene. Although no CRP mutant was available, the results indicated that CRP was a cAMP-binding receptor affecting gltA-2 transcription when the intracellular cAMP concentration increased. Thus, an overall model of CS regulation by C and/or N metabolism regulators and cAMP receptor protein was proposed.
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Affiliation(s)
- Cheng-Heng Liao
- Lab of Biosystems and Microanalysis, State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
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25
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Artificial citrate operon confers mineral phosphate solubilization ability to diverse fluorescent pseudomonads. PLoS One 2014; 9:e107554. [PMID: 25259527 PMCID: PMC4178029 DOI: 10.1371/journal.pone.0107554] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 08/18/2014] [Indexed: 01/28/2023] Open
Abstract
Citric acid is a strong acid with good cation chelating ability and can be very efficient in solubilizing mineral phosphates. Only a few phosphate solubilizing bacteria and fungi are known to secrete citric acids. In this work, we incorporated artificial citrate operon containing NADH insensitive citrate synthase (gltA1) and citrate transporter (citC) genes into the genome of six-plant growth promoting P. fluorescens strains viz., PfO-1, Pf5, CHAO1, P109, ATCC13525 and Fp315 using MiniTn7 transposon gene delivery system. Comprehensive biochemical characterization of the genomic integrants and their comparison with plasmid transformants of the same operon in M9 minimal medium reveals the highest amount of ∼7.6±0.41 mM citric and 29.95±2.8 mM gluconic acid secretion along with ∼43.2±3.24 mM intracellular citrate without affecting the growth of these P. fluorescens strains. All genomic integrants showed enhanced citric and gluconic acid secretion on Tris-Cl rock phosphate (TRP) buffered medium, which was sufficient to release 200–1000 µM Pi in TRP medium. This study demonstrates that MPS ability could be achieved in natural fluorescent pseudomonads by incorporation of artificial citrate operon not only as plasmid but also by genomic integration.
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Enzyme-substrate complexes of allosteric citrate synthase: evidence for a novel intermediate in substrate binding. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:2546-53. [PMID: 23954305 DOI: 10.1016/j.bbapap.2013.07.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 07/26/2013] [Accepted: 07/31/2013] [Indexed: 11/20/2022]
Abstract
The citrate synthase (CS) of Escherichia coli is an allosteric hexameric enzyme specifically inhibited by NADH. The crystal structure of wild type (WT) E. coli CS, determined by us previously, has no substrates bound, and part of the active site is in a highly mobile region that is shifted from the position needed for catalysis. The CS of Acetobacter aceti has a similar structure, but has been successfully crystallized with bound substrates: both oxaloacetic acid (OAA) and an analog of acetyl coenzyme A (AcCoA). We engineered a variant of E. coli CS wherein five amino acids in the mobile region have been replaced by those in the A. aceti sequence. The purified enzyme shows unusual kinetics with a low affinity for both substrates. Although the crystal structure without ligands is very similar to that of the WT enzyme (except in the mutated region), complexes are formed with both substrates and the allosteric inhibitor NADH. The complex with OAA in the active site identifies a novel OAA-binding residue, Arg306, which has no functional counterpart in other known CS-OAA complexes. This structure may represent an intermediate in a multi-step substrate binding process where Arg306 changes roles from OAA binding to AcCoA binding. The second complex has the substrate analog, S-carboxymethyl-coenzyme A, in the allosteric NADH-binding site and the AcCoA site is not formed. Additional CS variants unable to bind adenylates at the allosteric site show that this second complex is not a factor in positive allosteric activation of AcCoA binding.
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27
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Mullins EA, Kappock TJ. Crystal structures of Acetobacter aceti succinyl-coenzyme A (CoA):acetate CoA-transferase reveal specificity determinants and illustrate the mechanism used by class I CoA-transferases. Biochemistry 2012; 51:8422-34. [PMID: 23030530 DOI: 10.1021/bi300957f] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Coenzyme A (CoA)-transferases catalyze transthioesterification reactions involving acyl-CoA substrates, using an active-site carboxylate to form covalent acyl anhydride and CoA thioester adducts. Mechanistic studies of class I CoA-transferases suggested that acyl-CoA binding energy is used to accelerate rate-limiting acyl transfers by compressing the substrate thioester tightly against the catalytic glutamate [White, H., and Jencks, W. P. (1976) J. Biol. Chem. 251, 1688-1699]. The class I CoA-transferase succinyl-CoA:acetate CoA-transferase is an acetic acid resistance factor (AarC) with a role in a variant citric acid cycle in Acetobacter aceti. In an effort to identify residues involved in substrate recognition, X-ray crystal structures of a C-terminally His(6)-tagged form (AarCH6) were determined for several wild-type and mutant complexes, including freeze-trapped acetylglutamyl anhydride and glutamyl-CoA thioester adducts. The latter shows the acetate product bound to an auxiliary site that is required for efficient carboxylate substrate recognition. A mutant in which the catalytic glutamate was changed to an alanine crystallized in a closed complex containing dethiaacetyl-CoA, which adopts an unusual curled conformation. A model of the acetyl-CoA Michaelis complex demonstrates the compression anticipated four decades ago by Jencks and reveals that the nucleophilic glutamate is held at a near-ideal angle for attack as the thioester oxygen is forced into an oxyanion hole composed of Gly388 NH and CoA N2″. CoA is nearly immobile along its entire length during all stages of the enzyme reaction. Spatial and sequence conservation of key residues indicates that this mechanism is general among class I CoA-transferases.
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Affiliation(s)
- Elwood A Mullins
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907-2063, USA
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Mullins EA, Starks CM, Francois JA, Sael L, Kihara D, Kappock TJ. Formyl-coenzyme A (CoA):oxalate CoA-transferase from the acidophile Acetobacter aceti has a distinctive electrostatic surface and inherent acid stability. Protein Sci 2012; 21:686-96. [PMID: 22374910 DOI: 10.1002/pro.2054] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 01/26/2012] [Accepted: 02/20/2012] [Indexed: 11/09/2022]
Abstract
Bacterial formyl-CoA:oxalate CoA-transferase (FCOCT) and oxalyl-CoA decarboxylase work in tandem to perform a proton-consuming decarboxylation that has been suggested to have a role in generalized acid resistance. FCOCT is the product of uctB in the acidophilic acetic acid bacterium Acetobacter aceti. As expected for an acid-resistance factor, UctB remains folded at the low pH values encountered in the A. aceti cytoplasm. A comparison of crystal structures of FCOCTs and related proteins revealed few features in UctB that would distinguish it from nonacidophilic proteins and thereby account for its acid stability properties, other than a strikingly featureless electrostatic surface. The apparently neutral surface is a result of a "speckled" charge decoration, in which charged surface residues are surrounded by compensating charges but do not form salt bridges. A quantitative comparison among orthologs identified a pattern of residue substitution in UctB that may be a consequence of selection for protein stability by constant exposure to acetic acid. We suggest that this surface charge pattern, which is a distinctive feature of A. aceti proteins, creates a stabilizing electrostatic network without stiffening the protein or compromising protein-solvent interactions.
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Affiliation(s)
- Elwood A Mullins
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907, USA
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Chittori S, Savithri HS, Murthy MRN. Crystal structure of Salmonella typhimurium 2-methylcitrate synthase: Insights on domain movement and substrate specificity. J Struct Biol 2010; 174:58-68. [PMID: 20970504 DOI: 10.1016/j.jsb.2010.10.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2010] [Revised: 10/02/2010] [Accepted: 10/18/2010] [Indexed: 11/17/2022]
Abstract
2-Methylcitric acid (2-MCA) cycle is one of the well studied pathways for the utilization of propionate as a source of carbon and energy in bacteria such as Salmonella typhimurium and Escherichia coli. 2-Methylcitrate synthase (2-MCS) catalyzes the conversion of oxaloacetate and propionyl-CoA to 2-methylcitrate and CoA in the second step of 2-MCA cycle. Here, we report the X-ray crystal structure of S. typhimurium 2-MCS (StPrpC) at 2.4Å resolution and its functional characterization. StPrpC was found to utilize propionyl-CoA more efficiently than acetyl-CoA or butyryl-CoA. The polypeptide fold and the catalytic residues of StPrpC are conserved in citrate synthases (CSs) suggesting similarities in their functional mechanisms. In the triclinic P1 cell, StPrpC molecules were organized as decamers composed of five identical dimer units. In solution, StPrpC was in a dimeric form at low concentrations and was converted to larger oligomers at higher concentrations. CSs are usually dimeric proteins. In Gram-negative bacteria, a hexameric form, believed to be important for regulation of activity by NADH, is also observed. Structural comparisons with hexameric E. coli CS suggested that the key residues involved in NADH binding are not conserved in StPrpC. Structural comparison with the ligand free and bound states of CSs showed that StPrpC is in a nearly closed conformation despite the absence of bound ligands. It was found that the Tyr197 and Leu324 of StPrpC are structurally equivalent to the ligand binding residues His and Val, respectively, of CSs. These substitutions might determine the specificities for acyl-CoAs of these enzymes.
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Affiliation(s)
- Sagar Chittori
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
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Chittori S, Simanshu DK, Savithri HS, Murthy MRN. Preliminary X-ray crystallographic analysis of 2-methylcitrate synthase from Salmonella typhimurium. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:467-70. [PMID: 20383024 PMCID: PMC2852346 DOI: 10.1107/s1744309110007256] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 02/25/2010] [Indexed: 11/10/2022]
Abstract
Analysis of the genomic sequences of Escherichia coli and Salmonella typhimurium has revealed the presence of several homologues of the well studied citrate synthase (CS). One of these homologues has been shown to code for 2-methylcitrate synthase (2-MCS) activity. 2-MCS catalyzes one of the steps in the 2-methylcitric acid cycle found in these organisms for the degradation of propionate to pyruvate and succinate. In the present work, the gene coding for 2-MCS from S. typhimurium (StPrpC) was cloned in pRSET-C vector and overexpressed in E. coli. The protein was purified to homogeneity using Ni-NTA affinity chromatography. The purified protein was crystallized using the microbatch-under-oil method. The StPrpC crystals diffracted X-rays to 2.4 A resolution and belonged to the triclinic space group P1, with unit-cell parameters a = 92.068, b = 118.159, c = 120.659 A, alpha = 60.84, beta = 67.77, gamma = 81.92 degrees . Computation of rotation functions using the X-ray diffraction data shows that the protein is likely to be a decamer of identical subunits, unlike CSs, which are dimers or hexamers.
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Affiliation(s)
- Sagar Chittori
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - D. K. Simanshu
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - H. S. Savithri
- Department of Biochemistry, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - M. R. N. Murthy
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
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Kurz LC, Constantine CZ, Jiang H, Kappock TJ. The partial substrate dethiaacetyl-coenzyme A mimics all critical carbon acid reactions in the condensation half-reaction catalyzed by Thermoplasma acidophilum citrate synthase. Biochemistry 2009; 48:7878-91. [PMID: 19645419 DOI: 10.1021/bi9006447] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Citrate synthase (CS) performs two half-reactions: the mechanistically intriguing condensation of acetyl-CoA with oxaloacetate (OAA) to form citryl-CoA and the subsequent, slower hydrolysis of citryl-CoA that generally dominates steady-state kinetics. The condensation reaction requires the abstraction of a proton from the methyl carbon of acetyl-CoA to generate a reactive enolate intermediate. The carbanion of that intermediate then attacks the OAA carbonyl to furnish citryl-CoA, the initial product. Using stopped-flow and steady-state fluorescence methods, kinetic substrate isotope effects, and mutagenesis of active site residues, we show that all of the processes that occur in the condensation half-reaction performed by Thermoplasma acidophilum citrate synthase (TpCS) with the natural thioester substrate, acetyl-CoA, also occur with the ketone inhibitor dethiaacetyl-CoA. Free energy profiles demonstrate that the nonhydrolyzable product of the condensation reaction, dethiacitryl-CoA, forms a particularly stable complex with TpCS but not pig heart CS.
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Affiliation(s)
- Linda C Kurz
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Belien T, Joye IJ, Delcour JA, Courtin CM. Computational design-based molecular engineering of the glycosyl hydrolase family 11 B. subtilis XynA endoxylanase improves its acid stability. Protein Eng Des Sel 2009; 22:587-96. [DOI: 10.1093/protein/gzp024] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Abstract
The acetic acid bacteria (AAB) have important roles in food and beverage production, as well as in the bioproduction of industrial chemicals. In recent years, there have been major advances in understanding their taxonomy, molecular biology, and physiology, and in methods for their isolation and identification. AAB are obligate aerobes that oxidize sugars, sugar alcohols, and ethanol with the production of acetic acid as the major end product. This special type of metabolism differentiates them from all other bacteria. Recently, the AAB taxonomy has been strongly rearranged as new techniques using 16S rRNA sequence analysis have been introduced. Currently, the AAB are classified in ten genera in the family Acetobacteriaceae. AAB can not only play a positive role in the production of selected foods and beverages, but they can also spoil other foods and beverages. AAB occur in sugar- and alcohol-enriched environments. The difficulty of cultivation of AAB on semisolid media in the past resulted in poor knowledge of the species present in industrial processes. The first step of acetic acid production is the conversion of ethanol from a carbohydrate carried out by yeasts, and the second step is the oxidation of ethanol to acetic acid carried out by AAB. Vinegar is traditionally the product of acetous fermentation of natural alcoholic substrates. Depending on the substrate, vinegars can be classified as fruit, starch, or spirit substrate vinegars. Although a variety of bacteria can produce acetic acid, mostly members of Acetobacter, Gluconacetobacter, and Gluconobacter are used commercially. Industrial vinegar manufacturing processes fall into three main categories: slow processes, quick processes, and submerged processes. AAB also play an important role in cocoa production, which represents a significant means of income for some countries. Microbial cellulose, produced by AAB, possesses some excellent physical properties and has potential for many applications. Other products of biotransformations by AAB or their enzymes include 2-keto-L-gulonic acid, which is used for the production of vitamin C; D-tagatose, which is used as a bulking agent in food and a noncalorific sweetener; and shikimate, which is a key intermediate for a large number of antibiotics. Recently, for the first time, a pathogenic acetic acid bacterium was described, representing the newest and tenth genus of AAB.
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Affiliation(s)
- Peter Raspor
- Department of Food Science and Technology, University of Ljubljana, Ljubljana, Slovenia
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Nakano S, Fukaya M. Analysis of proteins responsive to acetic acid in Acetobacter: Molecular mechanisms conferring acetic acid resistance in acetic acid bacteria. Int J Food Microbiol 2008; 125:54-9. [DOI: 10.1016/j.ijfoodmicro.2007.05.015] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Revised: 05/08/2007] [Accepted: 05/16/2007] [Indexed: 11/26/2022]
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A specialized citric acid cycle requiring succinyl-coenzyme A (CoA):acetate CoA-transferase (AarC) confers acetic acid resistance on the acidophile Acetobacter aceti. J Bacteriol 2008; 190:4933-40. [PMID: 18502856 DOI: 10.1128/jb.00405-08] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Microbes tailor macromolecules and metabolism to overcome specific environmental challenges. Acetic acid bacteria perform the aerobic oxidation of ethanol to acetic acid and are generally resistant to high levels of these two membrane-permeable poisons. The citric acid cycle (CAC) is linked to acetic acid resistance in Acetobacter aceti by several observations, among them the oxidation of acetate to CO2 by highly resistant acetic acid bacteria and the previously unexplained role of A. aceti citrate synthase (AarA) in acetic acid resistance at a low pH. Here we assign specific biochemical roles to the other components of the A. aceti strain 1023 aarABC region. AarC is succinyl-coenzyme A (CoA):acetate CoA-transferase, which replaces succinyl-CoA synthetase in a variant CAC. This new bypass appears to reduce metabolic demand for free CoA, reliance upon nucleotide pools, and the likely effect of variable cytoplasmic pH upon CAC flux. The putative aarB gene is reassigned to SixA, a known activator of CAC flux. Carbon overflow pathways are triggered in many bacteria during metabolic limitation, which typically leads to the production and diffusive loss of acetate. Since acetate overflow is not feasible for A. aceti, a CO(2) loss strategy that allows acetic acid removal without substrate-level (de)phosphorylation may instead be employed. All three aar genes, therefore, support flux through a complete but unorthodox CAC that is needed to lower cytoplasmic acetate levels.
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Schaefer J, Jiang H, Ransome AE, Kappock TJ. Multiple active site histidine protonation states in Acetobacter aceti N5-carboxyaminoimidazole ribonucleotide mutase detected by REDOR NMR. Biochemistry 2007; 46:9507-12. [PMID: 17655332 PMCID: PMC2793534 DOI: 10.1021/bi700899q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Class I PurE (N5-carboxyaminoimidazole mutase) catalyzes a chemically unique mutase reaction. A working mechanistic hypothesis involves a histidine (His45 in Escherichia coli PurE) functioning as a general acid, but no evidence for multiple protonation states has been obtained. Solution NMR is a peerless tool for this task but has had limited application to enzymes, most of which are larger than its effective molecular size limit. Solid-state NMR is not subject to this limit. REDOR NMR studies of a 151 kDa complex of uniformly 15N-labeled Acetobacter aceti PurE (AaPurE) and the active site ligand [6-13C]citrate probed a single ionization equilibrium associated with the key histidine (AaPurE His59). In the AaPurE complex, the citrate central carboxylate C6 13C peak moves upfield, indicating diminution of negative charge, and broadens, indicating heterogeneity. Histidine 15N chemical shifts indicate His59 exists in approximately equimolar amounts of an Ndelta-unprotonated (pyridine-like) form and an Ndelta-protonated (pyrrole-like) form, each of which is approximately 4 A from citrate C6. The spectroscopic data are consistent with proton transfers involving His59 Ndelta that are invoked in the class I PurE mechanism.
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Affiliation(s)
- Jacob Schaefer
- Department of Chemistry, Washington University in St. Louis, St. Louis MO 63130-4899
| | - Hong Jiang
- Department of Chemistry, Washington University in St. Louis, St. Louis MO 63130-4899
| | - Aaron E. Ransome
- Department of Chemistry, Washington University in St. Louis, St. Louis MO 63130-4899
| | - T. Joseph Kappock
- Department of Chemistry, Washington University in St. Louis, St. Louis MO 63130-4899
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Starks CM, Francois JA, MacArthur KM, Heard BZ, Kappock TJ. Atomic-resolution crystal structure of thioredoxin from the acidophilic bacterium Acetobacter aceti. Protein Sci 2007; 16:92-8. [PMID: 17192591 PMCID: PMC2222842 DOI: 10.1110/ps.062519707] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The crystal structure of thioredoxin (AaTrx) from the acetic acid bacterium Acetobacter aceti was determined at 1 A resolution. This is currently the highest resolution crystal structure available for any thioredoxin. Thioredoxins facilitate thiol-disulfide exchange, a process that is expected to be slow at the low pH values encountered in the A. aceti cytoplasm. Despite the apparent need to function at low pH, neither the active site nor the surface charge distribution of AaTrx is notably different from that of Escherichia coli thioredoxin. Apparently the ancestral thioredoxin was sufficiently stable for use in A. aceti or the need to interact with multiple targets constrained the variation of surface residues. The AaTrx structure presented here provides a clear view of all ionizable protein moieties and waters, a first step in understanding how thiol-disulfide exchange might occur in a low pH cytoplasm, and is a basis for biophysical studies of the mechanism of acid-mediated unfolding. The high resolution of this structure should be useful for computational studies of thioredoxin function, protein structure and dynamics, and side-chain ionization.
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Affiliation(s)
- Courtney M Starks
- Department of Chemistry, Washington University in Saint Louis, Missouri 63130, USA
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