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Roy A, Karttunen M. A Molecular Dynamics Simulation Study of the Effects of βGln114 Mutation on the Dynamic Behavior of the Catalytic Site of the Tryptophan Synthase. J Chem Inf Model 2024; 64:983-1003. [PMID: 38291608 DOI: 10.1021/acs.jcim.3c01966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
L-tryptophan (l-Trp), a vital amino acid for the survival of various organisms, is synthesized by the enzyme tryptophan synthase (TS) in organisms such as eubacteria, archaebacteria, protista, fungi, and plantae. TS, a pyridoxal 5'-phosphate (PLP)-dependent enzyme, comprises α and β subunits that typically form an α2β2 tetramer. The enzyme's activity is regulated by the conformational switching of its α and β subunits between the open (T state) and closed (R state) conformations. Many microorganisms rely on TS for growth and replication, making the enzyme and the l-Trp biosynthetic pathway potential drug targets. For instance, Mycobacterium tuberculosis, Chlamydiae bacteria, Streptococcus pneumoniae, Francisella tularensis, Salmonella bacteria, and Cryptosporidium parasitic protozoa depend on l-Trp synthesis. Antibiotic-resistant salmonella strains have emerged, underscoring the need for novel drugs targeting the l-Trp biosynthetic pathway, especially for salmonella-related infections. A single amino acid mutation can significantly impact enzyme function, affecting stability, conformational dynamics, and active or allosteric sites. These changes influence interactions, catalytic activity, and protein-ligand/protein-protein interactions. This study focuses on the impact of mutating the βGln114 residue on the catalytic and allosteric sites of TS. Extensive molecular dynamics simulations were conducted on E(PLP), E(AEX1), E(A-A), and E(C3) forms of TS using the WT, βQ114A, and βQ114N versions. The results show that both the βQ114A and βQ114N mutations increase protein backbone root mean square deviation fluctuations, destabilizing all TS forms. Conformational and hydrogen bond analyses suggest the significance of βGln114 drifting away from cofactor/intermediates and forming hydrogen bonds with water molecules necessary for l-Trp biosynthesis. The βQ114A mutation creates a gap between βAla114 and cofactor/intermediates, hindering hydrogen bond formation due to short side chains and disrupting β-sites. Conversely, the βQ114N mutation positions βAsn114 closer to cofactor/intermediates, forming hydrogen bonds with O3 of cofactors/intermediates and nearby water molecules, potentially disrupting the l-Trp biosynthetic mechanism.
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Affiliation(s)
- Anupom Roy
- Department of Chemistry, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A5B7, Canada
| | - Mikko Karttunen
- Department of Chemistry, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A5B7, Canada
- Department of Physics and Astronomy, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A3K7, Canada
- The Centre of Advanced Materials and Biomaterials Research, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A5B7, Canada
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2
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Wang Y, Wang X, Niu S, Cheng W, Liu X, Min Y, Qiu Y, Ma L, Rao B, Zhu L. Improving the Activity of Tryptophan Synthetase via a Nucleic Acid Scaffold. Molecules 2023; 28:7272. [PMID: 37959692 PMCID: PMC10648251 DOI: 10.3390/molecules28217272] [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: 06/10/2023] [Revised: 09/17/2023] [Accepted: 09/25/2023] [Indexed: 11/15/2023] Open
Abstract
Tryptophan synthetase (TSase), which functions as a tetramer, is a typical enzyme with a substrate channel effect, and shows excellent performance in the production of non-standard amino acids, histamine, and other biological derivatives. Based on previous work, we fused a mutant CE protein (colistin of E. coli, a polypeptide with antibacterial activity) sequence with the sequence of TSase to explore whether its catalytic activity could be enhanced, and we also analyzed whether the addition of a DNA scaffold was a feasible strategy. Here, dCE (CE protein without DNase activity) protein tags were constructed and fused to the TrapA and TrapB subunits of TSase, and the whole cell was used for the catalytic reaction. The results showed that after the dCE protein tag was fused to the TrapB subunit, its whole cell catalytic activity increased by 50%. Next, the two subunits were expressed separately, and the proteins were bound in vitro to ensure equimolar combination between the two subunits. After the dCE label was fused to TrapB, the activity of TSase assembled with TrapA also improved. A series of experiments revealed that the enzyme fused with dCE9 showed higher activity than the wild-type protein. In general, the activity of assembly TSase was optimal when the temperature was 50 °C and the pH was about 9.0. After a long temperature treatment, the enzyme maintained good activity. With the addition of exogenous nucleic acid, the activity of the enzyme increased. The maximum yield was 0.58 g/L, which was almost three times that of the wild-type TSase (0.21 g/L). The recombinant TSase constructed in this study with dCE fusion had the advantages of higher heat resistance and higher activity, and confirmed the feasibility of adding a nucleic acid scaffold, providing a new idea for the improvement of structurally similar enzymes.
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Affiliation(s)
- Yaping Wang
- Hubei Biopesticide Engineering Research Center, Hubei Academy of Agricultural Sciences, Biopesticide Branch of Hubei Innovation Centre of Agricultural Science and Technology, Wuhan 430064, China
- State Key Laboratory of Biocatalysis and Enzyme, Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, Biology Faculty of Hubei University, Hubei University, Wuhan 430062, China
| | - Xiangyi Wang
- Hubei Biopesticide Engineering Research Center, Hubei Academy of Agricultural Sciences, Biopesticide Branch of Hubei Innovation Centre of Agricultural Science and Technology, Wuhan 430064, China
- State Key Laboratory of Biocatalysis and Enzyme, Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, Biology Faculty of Hubei University, Hubei University, Wuhan 430062, China
| | - Shuhui Niu
- Hubei Biopesticide Engineering Research Center, Hubei Academy of Agricultural Sciences, Biopesticide Branch of Hubei Innovation Centre of Agricultural Science and Technology, Wuhan 430064, China
- State Key Laboratory of Biocatalysis and Enzyme, Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, Biology Faculty of Hubei University, Hubei University, Wuhan 430062, China
| | - Wei Cheng
- Hubei Biopesticide Engineering Research Center, Hubei Academy of Agricultural Sciences, Biopesticide Branch of Hubei Innovation Centre of Agricultural Science and Technology, Wuhan 430064, China
- State Key Laboratory of Biocatalysis and Enzyme, Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, Biology Faculty of Hubei University, Hubei University, Wuhan 430062, China
| | - Xiaoyan Liu
- Hubei Biopesticide Engineering Research Center, Hubei Academy of Agricultural Sciences, Biopesticide Branch of Hubei Innovation Centre of Agricultural Science and Technology, Wuhan 430064, China
| | - Yong Min
- Hubei Biopesticide Engineering Research Center, Hubei Academy of Agricultural Sciences, Biopesticide Branch of Hubei Innovation Centre of Agricultural Science and Technology, Wuhan 430064, China
| | - Yimin Qiu
- Hubei Biopesticide Engineering Research Center, Hubei Academy of Agricultural Sciences, Biopesticide Branch of Hubei Innovation Centre of Agricultural Science and Technology, Wuhan 430064, China
| | - Lixin Ma
- State Key Laboratory of Biocatalysis and Enzyme, Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei Key Laboratory of Industrial Biotechnology, Biology Faculty of Hubei University, Hubei University, Wuhan 430062, China
| | - Ben Rao
- Hubei Biopesticide Engineering Research Center, Hubei Academy of Agricultural Sciences, Biopesticide Branch of Hubei Innovation Centre of Agricultural Science and Technology, Wuhan 430064, China
| | - Lei Zhu
- Hubei Biopesticide Engineering Research Center, Hubei Academy of Agricultural Sciences, Biopesticide Branch of Hubei Innovation Centre of Agricultural Science and Technology, Wuhan 430064, China
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3
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Yang J, Zhang L, Qiao W, Luo Y. Mycobacterium tuberculosis: Pathogenesis and therapeutic targets. MedComm (Beijing) 2023; 4:e353. [PMID: 37674971 PMCID: PMC10477518 DOI: 10.1002/mco2.353] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 07/31/2023] [Accepted: 08/03/2023] [Indexed: 09/08/2023] Open
Abstract
Tuberculosis (TB) remains a significant public health concern in the 21st century, especially due to drug resistance, coinfection with diseases like immunodeficiency syndrome (AIDS) and coronavirus disease 2019, and the lengthy and costly treatment protocols. In this review, we summarize the pathogenesis of TB infection, therapeutic targets, and corresponding modulators, including first-line medications, current clinical trial drugs and molecules in preclinical assessment. Understanding the mechanisms of Mycobacterium tuberculosis (Mtb) infection and important biological targets can lead to innovative treatments. While most antitubercular agents target pathogen-related processes, host-directed therapy (HDT) modalities addressing immune defense, survival mechanisms, and immunopathology also hold promise. Mtb's adaptation to the human host involves manipulating host cellular mechanisms, and HDT aims to disrupt this manipulation to enhance treatment effectiveness. Our review provides valuable insights for future anti-TB drug development efforts.
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Affiliation(s)
- Jiaxing Yang
- Center of Infectious Diseases and State Key Laboratory of Biotherapy, West China HospitalSichuan UniversityChengduChina
| | - Laiying Zhang
- Center of Infectious Diseases and State Key Laboratory of Biotherapy, West China HospitalSichuan UniversityChengduChina
| | - Wenliang Qiao
- Department of Thoracic Surgery, West China HospitalSichuan UniversityChengduSichuanChina
- Lung Cancer Center, West China HospitalSichuan UniversityChengduSichuanChina
| | - Youfu Luo
- Center of Infectious Diseases and State Key Laboratory of Biotherapy, West China HospitalSichuan UniversityChengduChina
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4
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Ghosh RK, Hilario E, Chang CEA, Mueller LJ, Dunn MF. Allosteric regulation of substrate channeling: Salmonella typhimurium tryptophan synthase. Front Mol Biosci 2022; 9:923042. [PMID: 36172042 PMCID: PMC9512447 DOI: 10.3389/fmolb.2022.923042] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 08/11/2022] [Indexed: 11/13/2022] Open
Abstract
The regulation of the synthesis of L-tryptophan (L-Trp) in enteric bacteria begins at the level of gene expression where the cellular concentration of L-Trp tightly controls expression of the five enzymes of the Trp operon responsible for the synthesis of L-Trp. Two of these enzymes, trpA and trpB, form an αββα bienzyme complex, designated as tryptophan synthase (TS). TS carries out the last two enzymatic processes comprising the synthesis of L-Trp. The TS α-subunits catalyze the cleavage of 3-indole D-glyceraldehyde 3′-phosphate to indole and D-glyceraldehyde 3-phosphate; the pyridoxal phosphate-requiring β-subunits catalyze a nine-step reaction sequence to replace the L-Ser hydroxyl by indole giving L-Trp and a water molecule. Within αβ dimeric units of the αββα bienzyme complex, the common intermediate indole is channeled from the α site to the β site via an interconnecting 25 Å-long tunnel. The TS system provides an unusual example of allosteric control wherein the structures of the nine different covalent intermediates along the β-reaction catalytic path and substrate binding to the α-site provide the allosteric triggers for switching the αββα system between the open (T) and closed (R) allosteric states. This triggering provides a linkage that couples the allosteric conformational coordinate to the covalent chemical reaction coordinates at the α- and β-sites. This coupling drives the α- and β-sites between T and R conformations to achieve regulation of substrate binding and/or product release, modulation of the α- and β-site catalytic activities, prevention of indole escape from the confines of the active sites and the interconnecting tunnel, and synchronization of the α- and β-site catalytic activities. Here we review recent advances in the understanding of the relationships between structure, function, and allosteric regulation of the complex found in Salmonella typhimurium.
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Affiliation(s)
- Rittik K. Ghosh
- Department of Biochemistry, University of California, Riverside, Riverside, CA, United States
| | - Eduardo Hilario
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States
| | - Chia-en A. Chang
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States
| | - Leonard J. Mueller
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States
- *Correspondence: Leonard J. Mueller, ; Michael F. Dunn,
| | - Michael F. Dunn
- Department of Biochemistry, University of California, Riverside, Riverside, CA, United States
- *Correspondence: Leonard J. Mueller, ; Michael F. Dunn,
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5
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Ghosh RK, Hilario E, Liu V, Wang Y, Niks D, Holmes JB, Sakhrani VV, Mueller LJ, Dunn MF. Mutation of βGln114 to Ala Alters the Stabilities of Allosteric States in Tryptophan Synthase Catalysis. Biochemistry 2021; 60:3173-3186. [PMID: 34595921 DOI: 10.1021/acs.biochem.1c00383] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The tryptophan synthase (TS) bienzyme complexes found in bacteria, yeasts, and molds are pyridoxal 5'-phosphate (PLP)-requiring enzymes that synthesize l-Trp. In the TS catalytic cycle, switching between the open and closed states of the α- and β-subunits via allosteric interactions is key to the efficient conversion of 3-indole-d-glycerol-3'-phosphate and l-Ser to l-Trp. In this process, the roles played by β-site residues proximal to the PLP cofactor have not yet been fully established. βGln114 is one such residue. To explore the roles played by βQ114, we conducted a detailed investigation of the βQ114A mutation on the structure and function of tryptophan synthase. Initial steady-state kinetic and static ultraviolet-visible spectroscopic analyses showed the Q to A mutation impairs catalytic activity and alters the stabilities of intermediates in the β-reaction. Therefore, we conducted X-ray structural and solid-state nuclear magnetic resonance spectroscopic studies to compare the wild-type and βQ114A mutant enzymes. These comparisons establish that the protein structural changes are limited to the Gln to Ala replacement, the loss of hydrogen bonds among the side chains of βGln114, βAsn145, and βArg148, and the inclusion of waters in the cavity created by substitution of the smaller Ala side chain. Because the conformations of the open and closed allosteric states are not changed by the mutation, we hypothesize that the altered properties arise from the lost hydrogen bonds that alter the relative stabilities of the open (βT state) and closed (βR state) conformations of the β-subunit and consequently alter the distribution of intermediates along the β-subunit catalytic path.
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Affiliation(s)
- Rittik K Ghosh
- Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Eduardo Hilario
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Viktoriia Liu
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Yangyang Wang
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Dimitri Niks
- Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Jacob B Holmes
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Varun V Sakhrani
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Leonard J Mueller
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Michael F Dunn
- Department of Biochemistry, University of California, Riverside, California 92521, United States
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6
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Michalska K, Wellington S, Maltseva N, Jedrzejczak R, Selem-Mojica N, Rosas-Becerra LR, Barona-Gómez F, Hung DT, Joachimiak A. Catalytically impaired TrpA subunit of tryptophan synthase from Chlamydia trachomatis is an allosteric regulator of TrpB. Protein Sci 2021; 30:1904-1918. [PMID: 34107106 PMCID: PMC8376405 DOI: 10.1002/pro.4143] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 11/10/2022]
Abstract
Intracellular growth and pathogenesis of Chlamydia species is controlled by the availability of tryptophan, yet the complete biosynthetic pathway for l‐Trp is absent among members of the genus. Some representatives, however, preserve genes encoding tryptophan synthase, TrpAB – a bifunctional enzyme catalyzing the last two steps in l‐Trp synthesis. TrpA (subunit α) converts indole‐3‐glycerol phosphate into indole and glyceraldehyde‐3‐phosphate (α reaction). The former compound is subsequently used by TrpB (subunit β) to produce l‐Trp in the presence of l‐Ser and a pyridoxal 5′‐phosphate cofactor (β reaction). Previous studies have indicated that in Chlamydia, TrpA has lost its catalytic activity yet remains associated with TrpB to support the β reaction. Here, we provide detailed analysis of the TrpAB from C. trachomatis D/UW‐3/CX, confirming that accumulation of mutations in the active site of TrpA renders it enzymatically inactive, despite the conservation of the catalytic residues. We also show that TrpA remains a functional component of the TrpAB complex, increasing the activity of TrpB by four‐fold. The side chain of non‐conserved βArg267 functions as cation effector, potentially rendering the enzyme less susceptible to the solvent ion composition. The observed structural and functional changes detected herein were placed in a broader evolutionary and genomic context, allowing identification of these mutations in relation to their trp gene contexts in which they occur. Moreover, in agreement with the in vitro data, partial relaxation of purifying selection for TrpA, but not for TrpB, was detected, reinforcing a partial loss of TrpA functions during the course of evolution. PDB Code(s): 6V82;
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Affiliation(s)
- Karolina Michalska
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, Illinois, USA.,Structural Biology Center, X-ray Science Division, Argonne National Laboratory, Argonne, Illinois, USA
| | - Samantha Wellington
- Department of Genetics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - Natalia Maltseva
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, Illinois, USA
| | - Robert Jedrzejczak
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, Illinois, USA
| | - Nelly Selem-Mojica
- Evolution of Metabolic Diversity Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav, Mexico
| | - L Rodrigo Rosas-Becerra
- Evolution of Metabolic Diversity Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav, Mexico
| | - Francisco Barona-Gómez
- Evolution of Metabolic Diversity Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav, Mexico
| | - Deborah T Hung
- Department of Genetics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - Andrzej Joachimiak
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, Illinois, USA.,Structural Biology Center, X-ray Science Division, Argonne National Laboratory, Argonne, Illinois, USA.,Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
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7
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Phillips RS, Harris AP. Structural Basis of the Stereochemistry of Inhibition of Tryptophan Synthase by Tryptophan and Derivatives. Biochemistry 2021; 60:231-244. [PMID: 33428374 DOI: 10.1021/acs.biochem.0c00635] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have examined the reaction of Salmonella enterica serovar typhimurium tryptophan (Trp) synthase α2β2 complex with l-Trp, d-Trp, oxindolyl-l-alanine (OIA), and dioxindolyl-l-alanine (DOA) in the presence of disodium (dl)-α-glycerol phosphate (GP), using stopped-flow spectrophotometry and X-ray crystallography. All structures contained the d-isomer of GP bound at the α-active site. (3S)-OIA reacts with the pyridoxal-5'-phosphate (PLP) of Trp synthase to form a mixture of external aldimine and quinonoid complexes. The α-carboxylate of OIA rotates about 90° to become planar with the PLP when the quinonoid complex is formed, resulting in a conformational change in the loop of residues 110-115. The COMM domain of the Trp synthase-OIA complex is found as a mixture of two conformations. The (3R)-diastereomer of DOA binds about 5-fold more tightly than (3S)-OIA and also forms a mixture of aldimine and quinonoid complexes. DOA forms an additional H-bond between the 3-OH of DOA and βLys-87. l-Trp does not form a covalent complex with the PLP of Trp synthase. However, d-Trp forms a mixture of two external aldimine complexes which differ in the orientation of the α-carboxylate. In one conformation, the α-carboxylate is in the plane of the PLP, while in the other conformation, the α-carboxylate is perpendicular to the PLP plane. These results confirm that the stereochemistry of the transient indolenine quinonoid intermediate in the mechanism of Trp synthase is (3S) and demonstrate the linkage between aldimine and quinonoid reaction intermediates in the β-active site and allosteric communications with the α-active site.
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Affiliation(s)
- Robert S Phillips
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, United States
| | - Austin P Harris
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
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8
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Watkins-Dulaney E, Straathof S, Arnold F. Tryptophan Synthase: Biocatalyst Extraordinaire. Chembiochem 2021; 22:5-16. [PMID: 32677310 PMCID: PMC7935429 DOI: 10.1002/cbic.202000379] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/15/2020] [Indexed: 12/23/2022]
Abstract
Tryptophan synthase (TrpS) has emerged as a paragon of noncanonical amino acid (ncAA) synthesis and is an ideal biocatalyst for synthetic and biological applications. TrpS catalyzes an irreversible, C-C bond-forming reaction between indole and serine to make l-tryptophan; native TrpS complexes possess fairly broad specificity for indole analogues, but are difficult to engineer to extend substrate scope or to confer other useful properties due to allosteric constraints and their heterodimeric structure. Directed evolution freed the catalytically relevant TrpS β-subunit (TrpB) from allosteric regulation by its TrpA partner and has enabled dramatic expansion of the enzyme's substrate scope. This review examines the long and storied career of TrpS from the perspective of its application in ncAA synthesis and biocatalytic cascades.
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Affiliation(s)
- Ella Watkins-Dulaney
- Division of Biology and Biological Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA 91125, USA
| | - Sabine Straathof
- Division of Chemistry and Chemical Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA 91125, USA
| | - Frances Arnold
- Division of Biology and Biological Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA 91125, USA
- Division of Chemistry and Chemical Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA 91125, USA
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9
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Loutchko D, Flechsig H. Allosteric communication in molecular machines via information exchange: what can be learned from dynamical modeling. Biophys Rev 2020; 12:443-452. [PMID: 32198636 DOI: 10.1007/s12551-020-00667-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 02/25/2020] [Indexed: 02/07/2023] Open
Abstract
Allosteric regulation is crucial for the operation of protein machines and molecular motors. A major challenge is to characterize and quantify the information exchange underlying allosteric communication between remote functional sites in a protein, and to identify the involved relevant pathways. We review applications of two topical approaches of dynamical protein modeling, a kinetic-based single-molecule stochastic model, which employs information thermodynamics to quantify allosteric interactions, and structure-based coarse-grained modeling to characterize intra-molecular couplings in terms of conformational motions and propagating mechanical strain. Both descriptions resolve the directionality of allosteric responses within a protein, emphasizing the concept of causality as the principal hallmark of protein allostery. We discuss the application of techniques from information thermodynamics to dynamic protein elastic networks and evolutionary designed model structures, and the ramifications for protein allostery.
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Affiliation(s)
- Dimitri Loutchko
- Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8561, Japan
| | - Holger Flechsig
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa, 920-1192, Japan.
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10
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Michalska K, Chang C, Maltseva NI, Jedrzejczak R, Robertson GT, Gusovsky F, McCarren P, Schreiber SL, Nag PP, Joachimiak A. Allosteric inhibitors of Mycobacterium tuberculosis tryptophan synthase. Protein Sci 2020; 29:779-788. [PMID: 31930594 PMCID: PMC7020977 DOI: 10.1002/pro.3825] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 01/07/2020] [Accepted: 01/08/2020] [Indexed: 12/13/2022]
Abstract
Global dispersion of multidrug resistant bacteria is very common and evolution of antibiotic-resistance is occurring at an alarming rate, presenting a formidable challenge for humanity. The development of new therapeuthics with novel molecular targets is urgently needed. Current drugs primarily affect protein, nucleic acid, and cell wall synthesis. Metabolic pathways, including those involved in amino acid biosynthesis, have recently sparked interest in the drug discovery community as potential reservoirs of such novel targets. Tryptophan biosynthesis, utilized by bacteria but absent in humans, represents one of the currently studied processes with a therapeutic focus. It has been shown that tryptophan synthase (TrpAB) is required for survival of Mycobacterium tuberculosis in macrophages and for evading host defense, and therefore is a promising drug target. Here we present crystal structures of TrpAB with two allosteric inhibitors of M. tuberculosis tryptophan synthase that belong to sulfolane and indole-5-sulfonamide chemical scaffolds. We compare our results with previously reported structural and biochemical studies of another, azetidine-containing M. tuberculosis tryptophan synthase inhibitor. This work shows how structurally distinct ligands can occupy the same allosteric site and make specific interactions. It also highlights the potential benefit of targeting more variable allosteric sites of important metabolic enzymes.
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Affiliation(s)
- Karolina Michalska
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and EngineeringUniversity of ChicagoChicagoIllinois
- Structural Biology Center, X‐ray Science DivisionArgonne National LaboratoryArgonneIllinois
| | - Changsoo Chang
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and EngineeringUniversity of ChicagoChicagoIllinois
- Structural Biology Center, X‐ray Science DivisionArgonne National LaboratoryArgonneIllinois
| | - Natalia I. Maltseva
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and EngineeringUniversity of ChicagoChicagoIllinois
- Structural Biology Center, X‐ray Science DivisionArgonne National LaboratoryArgonneIllinois
| | - Robert Jedrzejczak
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and EngineeringUniversity of ChicagoChicagoIllinois
- Structural Biology Center, X‐ray Science DivisionArgonne National LaboratoryArgonneIllinois
| | - Gregory T. Robertson
- Colorado State UniversityMycobacteria Research Laboratories, Department of Microbiology, Immunology and PathologyFort CollinsColorado
| | | | | | | | - Partha P. Nag
- Broad Institute of MIT and HarvardCambridgeMassachusetts
| | - Andrzej Joachimiak
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and EngineeringUniversity of ChicagoChicagoIllinois
- Structural Biology Center, X‐ray Science DivisionArgonne National LaboratoryArgonneIllinois
- Department of Biochemistry and Molecular BiologyUniversity of ChicagoChicagoIllinois
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Michalska K, Gale J, Joachimiak G, Chang C, Hatzos-Skintges C, Nocek B, Johnston SE, Bigelow L, Bajrami B, Jedrzejczak RP, Wellington S, Hung DT, Nag PP, Fisher SL, Endres M, Joachimiak A. Conservation of the structure and function of bacterial tryptophan synthases. IUCRJ 2019; 6:649-664. [PMID: 31316809 PMCID: PMC6608616 DOI: 10.1107/s2052252519005955] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 04/29/2019] [Indexed: 06/10/2023]
Abstract
Tryptophan biosynthesis is one of the most characterized processes in bacteria, in which the enzymes from Salmonella typhimurium and Escherichia coli serve as model systems. Tryptophan synthase (TrpAB) catalyzes the final two steps of tryptophan biosynthesis in plants, fungi and bacteria. This pyridoxal 5'-phosphate (PLP)-dependent enzyme consists of two protein chains, α (TrpA) and β (TrpB), functioning as a linear αββα heterotetrameric complex containing two TrpAB units. The reaction has a complicated, multistep mechanism resulting in the β-replacement of the hydroxyl group of l-serine with an indole moiety. Recent studies have shown that functional TrpAB is required for the survival of pathogenic bacteria in macrophages and for evading host defense. Therefore, TrpAB is a promising target for drug discovery, as its orthologs include enzymes from the important human pathogens Streptococcus pneumoniae, Legionella pneumophila and Francisella tularensis, the causative agents of pneumonia, legionnaires' disease and tularemia, respectively. However, specific biochemical and structural properties of the TrpABs from these organisms have not been investigated. To fill the important phylogenetic gaps in the understanding of TrpABs and to uncover unique features of TrpAB orthologs to spearhead future drug-discovery efforts, the TrpABs from L. pneumophila, F. tularensis and S. pneumoniae have been characterized. In addition to kinetic properties and inhibitor-sensitivity data, structural information gathered using X-ray crystallo-graphy is presented. The enzymes show remarkable structural conservation, but at the same time display local differences in both their catalytic and allosteric sites that may be responsible for the observed differences in catalysis and inhibitor binding. This functional dissimilarity may be exploited in the design of species-specific enzyme inhibitors.
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Affiliation(s)
- Karolina Michalska
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, IL 60367, USA
- Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Jennifer Gale
- Broad Institute of MIT and Harvard, Cambridge, MA 02141, USA
| | - Grazyna Joachimiak
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Changsoo Chang
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, IL 60367, USA
- Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Catherine Hatzos-Skintges
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, IL 60367, USA
| | - Boguslaw Nocek
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, IL 60367, USA
- Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | | | - Lance Bigelow
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Besnik Bajrami
- Broad Institute of MIT and Harvard, Cambridge, MA 02141, USA
| | - Robert P. Jedrzejczak
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, IL 60367, USA
- Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | | | - Deborah T. Hung
- Broad Institute of MIT and Harvard, Cambridge, MA 02141, USA
| | - Partha P. Nag
- Broad Institute of MIT and Harvard, Cambridge, MA 02141, USA
| | | | - Michael Endres
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Andrzej Joachimiak
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, IL 60367, USA
- Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60367, USA
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Loutchko D, Eisbach M, Mikhailov AS. Stochastic thermodynamics of a chemical nanomachine: The channeling enzyme tryptophan synthase. J Chem Phys 2017; 146:025101. [DOI: 10.1063/1.4973544] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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13
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Loutchko D, Gonze D, Mikhailov AS. Single-Molecule Stochastic Analysis of Channeling Enzyme Tryptophan Synthase. J Phys Chem B 2016; 120:2179-86. [PMID: 26863529 DOI: 10.1021/acs.jpcb.5b12229] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The channeling enzyme tryptophan synthase provides a paradigmatic example of a chemical nanomachine. It possesses two active centers and, as a single molecule, catalyzes 13 different reaction steps with a complex pattern of allosteric regulation and with an intermediate product channeled from one active center to another. Here, the first single-molecule stochastic model of the enzyme is proposed and analyzed. All its transition rate constants were deduced from the experimental data available, and no fitting parameters were thus employed. Numerical simulations reveal strong correlations in the states of the active centers and the emergent synchronization of intramolecular processes in tryptophan synthase.
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Affiliation(s)
- Dimitri Loutchko
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society , 14195 Berlin, Germany
| | - Didier Gonze
- Unité de Chronobiologie théorique, Faculté des Sciences, Université Libre de Bruxelles , 1050 Brussels, Belgium
| | - Alexander S Mikhailov
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society , 14195 Berlin, Germany.,Department of Mathematical and Life Sciences, Hiroshima University , 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
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14
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Catalytic roles of βLys87 in tryptophan synthase: (15)N solid state NMR studies. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1194-9. [PMID: 25688830 DOI: 10.1016/j.bbapap.2015.02.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Revised: 02/06/2015] [Accepted: 02/09/2015] [Indexed: 10/24/2022]
Abstract
The proposed mechanism for tryptophan synthase shows βLys87 playing multiple catalytic roles: it bonds to the PLP cofactor, activates C4' for nucleophilic attack via a protonated Schiff base nitrogen, and abstracts and returns protons to PLP-bound substrates (i.e. acid-base catalysis). ε-¹⁵N-lysine TS was prepared to access the protonation state of βLys87 using ¹⁵N solid-state nuclear magnetic resonance (SSNMR) spectroscopy for three quasi-stable intermediates along the reaction pathway. These experiments establish that the protonation state of the ε-amino group switches between protonated and neutral states as the β-site undergoes conversion from one intermediate to the next during catalysis, corresponding to mechanistic steps where this lysine residue has been anticipated to play alternating acid and base catalytic roles that help steer reaction specificity in tryptophan synthase catalysis. This article is part of a Special Issue entitled: Cofactor-dependent proteins: evolution, chemical diversity and bio-applications. Guest Editors: Andrea Mozzarelli and Loredano Pollegioni.
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15
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Niks D, Hilario E, Dierkers A, Ngo H, Borchardt D, Neubauer TJ, Fan L, Mueller LJ, Dunn MF. Allostery and substrate channeling in the tryptophan synthase bienzyme complex: evidence for two subunit conformations and four quaternary states. Biochemistry 2013; 52:6396-411. [PMID: 23952479 DOI: 10.1021/bi400795e] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The allosteric regulation of substrate channeling in tryptophan synthase involves ligand-mediated allosteric signaling that switches the α- and β-subunits between open (low activity) and closed (high activity) conformations. This switching prevents the escape of the common intermediate, indole, and synchronizes the α- and β-catalytic cycles. (19)F NMR studies of bound α-site substrate analogues, N-(4'-trifluoromethoxybenzoyl)-2-aminoethyl phosphate (F6) and N-(4'-trifluoromethoxybenzenesulfonyl)-2-aminoethyl phosphate (F9), were found to be sensitive NMR probes of β-subunit conformation. Both the internal and external aldimine F6 complexes gave a single bound peak at the same chemical shift, while α-aminoacrylate and quinonoid F6 complexes all gave a different bound peak shifted by +1.07 ppm. The F9 complexes exhibited similar behavior, but with a corresponding shift of -0.12 ppm. X-ray crystal structures show the F6 and F9 CF3 groups located at the α-β subunit interface and report changes in both the ligand conformation and the surrounding protein microenvironment. Ab initio computational modeling suggests that the change in (19)F chemical shift results primarily from changes in the α-site ligand conformation. Structures of α-aminoacrylate F6 and F9 complexes and quinonoid F6 and F9 complexes show the α- and β-subunits have closed conformations wherein access of ligands into the α- and β-sites from solution is blocked. Internal and external aldimine structures show the α- and β-subunits with closed and open global conformations, respectively. These results establish that β-subunits exist in two global conformational states, designated open, where the β-sites are freely accessible to substrates, and closed, where the β-site portal into solution is blocked. Switching between these conformations is critically important for the αβ-catalytic cycle.
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Affiliation(s)
- Dimitri Niks
- Department of Biochemistry, University of California at Riverside , Riverside, California 92521, United States
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Lee J, Goodey NM. Catalytic contributions from remote regions of enzyme structure. Chem Rev 2011; 111:7595-624. [PMID: 21923192 DOI: 10.1021/cr100042n] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Jeeyeon Lee
- Department of Chemistry, 413 Wartik Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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Aitken SM, Lodha PH, Morneau DJK. The enzymes of the transsulfuration pathways: active-site characterizations. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1511-7. [PMID: 21435402 DOI: 10.1016/j.bbapap.2011.03.006] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 03/03/2011] [Accepted: 03/09/2011] [Indexed: 11/19/2022]
Abstract
The diversity of reactions catalyzed by enzymes reliant on pyridoxal 5'-phosphate (PLP) demonstrates the catalytic versatility of this cofactor and the plasticity of the protein scaffolds of the major fold types of PLP-dependent enzymes. The enzymes of the transsulfuration (cystathionine γ-synthase and cystathionine β-lyase) and reverse transsulfuration (cystathionine β-synthase and cystathionine γ-lyase) pathways interconvert l-cysteine and l-homocysteine, the immediate precursor of l-methionine, in plants/bacteria and yeast/animals, respectively. These enzymes provide a useful model system for investigation of the mechanisms of substrate and reaction specificity in PLP-dependent enzymes as they catalyze distinct side chain rearrangements of similar amino acid substrates. Exploration of the underlying factors that enable enzymes to control the substrate and reaction specificity of this cofactor will enable the engineering of these properties and the development of therapeutics and antimicrobial compounds. Recent studies probing the role of active-site residues, of the enzymes of the transsulfuration pathways, as determinants of substrate and reaction specificity are the subject of this review. This article is part of a Special Issue entitled: Pyridoxal Phosphate Enzymology.
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Affiliation(s)
- Susan M Aitken
- Department of Biology, Carleton University, Ottowa, Canada.
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Lai J, Niks D, Wang Y, Domratcheva T, Barends TRM, Schwarz F, Olsen RA, Elliott DW, Fatmi MQ, Chang CEA, Schlichting I, Dunn MF, Mueller LJ. X-ray and NMR Crystallography in an Enzyme Active Site: The Indoline Quinonoid Intermediate in Tryptophan Synthase. J Am Chem Soc 2010; 133:4-7. [DOI: 10.1021/ja106555c] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jinfeng Lai
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Dimitri Niks
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Yachong Wang
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Tatiana Domratcheva
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Thomas R. M. Barends
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Friedrich Schwarz
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Ryan A. Olsen
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Douglas W. Elliott
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - M. Qaiser Fatmi
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Chia-en A. Chang
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Ilme Schlichting
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Michael F. Dunn
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Leonard J. Mueller
- Departments of Chemistry and Biochemistry, University of California, Riverside, California 92521, United States, and Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
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Tian H, Guan R, Salsi E, Campanini B, Bettati S, Kumar VP, Karsten WE, Mozzarelli A, Cook PF. Identification of the structural determinants for the stability of substrate and aminoacrylate external Schiff bases in O-acetylserine sulfhydrylase-A. Biochemistry 2010; 49:6093-103. [PMID: 20550197 DOI: 10.1021/bi100473v] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
O-Acetylserine sulfhydrylase is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the final step in the cysteine biosynthetic pathway in enteric bacteria and plants, the replacement of the beta-acetoxy group of O-acetyl-L-serine (OAS) by a thiol to give L-cysteine. Previous studies of the K41A mutant enzyme showed L-methionine bound in an external Schiff base (ESB) linkage to PLP as the enzyme was isolated. The mutant enzyme exists in a closed form, optimizing the orientation of the cofactor PLP and properly positioning active site functional groups for reaction. The trigger for closing the active site upon formation of the ESB is thought to be interaction of the substrate alpha-carboxylate with the substrate-binding loop comprised of T68, S69, G70, and N71, and Q142, which is positioned above the cofactor as one looks into the active site. To probe the contribution of these residues to the active site closing and orientation of PLP in the ESB, T68, S69, N71, and Q142 were changed to alanine. Absorbance, fluorescence, near UV-visible CD, and (31)P NMR spectral studies and pre-steady state kinetic studies were used to characterize the mutant enzymes. All of the mutations affect closure of the active site, but to differing extents. In addition, the site appears to be more hydrophilic given that the ESBs do not exhibit a significant amount of the enolimine tautomer. No buildup of the alpha-aminoacrylate intermediate (AA) is observed for the T68A and Q142A mutant enzymes. However, pyruvate is produced at a rate much greater than that of the wild-type enzyme. Data suggest that T68 and Q142 play a role in stabilizing the AA. Both residues donate a hydrogen bond to one of the carboxylate oxygens of the methionine ESB and may also be responsible for the proper orientation of the ESB to generate the AA. The S69A and N71A mutants exhibit formation of the AA, but the rate constant for its formation from the ESB is decreased by 1 order of magnitude compared to that of the wild type. S69 donates a hydrogen bond to the substrate carboxylate in the ESB, while N71 donates hydrogen bonds to O3' of the cofactor and the carboxylate of the ESB; these side chains may also affect the orientation of the ESB. Data suggest that interaction of intermediates with the substrate-binding loop and Q142 gives a properly aligned Michaelis complex and facilitates the beta-elimination reaction.
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Affiliation(s)
- Hui Tian
- Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Norman, Oklahoma 73018, USA
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Residue N84 of Yeast Cystathionine β-Synthase is a Determinant of Reaction Specificity. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2010; 1804:1424-31. [DOI: 10.1016/j.bbapap.2010.02.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2009] [Revised: 01/28/2010] [Accepted: 02/12/2010] [Indexed: 11/23/2022]
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Dierkers AT, Niks D, Schlichting I, Dunn MF. Tryptophan synthase: structure and function of the monovalent cation site. Biochemistry 2009; 48:10997-1010. [PMID: 19848417 DOI: 10.1021/bi9008374] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The monovalent cation (MVC) site of the tryptophan synthase from Salmonella typhimurium plays essential roles in catalysis and in the regulation of substrate channeling. In vitro, MVCs affect the equilibrium distribution of intermediates formed in the reaction of l-Ser with the alpha(2)beta(2) complex; the MVC-free, Cs(+)-bound, and NH(4)(+)-bound enzymes stabilize the alpha-aminoacrylate species, E(A-A), while Na(+) binding stabilizes the l-Ser external aldimine species, E(Aex(1)). Two probes of beta-site reactivity and conformation were used herein, the reactive indole analogue, indoline, and the l-Trp analogue, l-His. MVC-bound E(A-A) reacts rapidly with indoline to give the indoline quinonoid species, E(Q)(indoline), which slowly converts to dihydroiso-l-tryptophan. MVC-free E(A-A) gives very little E(Q)(indoline), and turnover is strongly impaired; the fraction of E(Q)(indoline) formed is <3.5% of that given by the Na(+)-bound form. The reaction of l-Ser with the MVC-free internal aldimine species, E(Ain), initially gives small amounts of an active E(A-A) which converts to an inactive species on a slower, conformational, time scale. This inactivation is abolished by the binding of MVCs. The inactive E(A-A) appears to have a closed beta-subunit conformation with an altered substrate binding site that is different from the known conformations of tryptophan synthase. Reaction of l-His with E(Ain) gives an equilibrating mixture of external aldimine and quinonoid species, E(Aex)(his) and E(Q)(his). The MVC-free and Na(+) forms of the enzyme gave trace amounts of E(Q)(his) ( approximately 1% of the beta-sites). The Cs(+) and NH(4)(+) forms gave approximately 17 and approximately 14%, respectively. The reactivity of MVC-free E(Ain) was restored by the binding of an alpha-site ligand. These studies show MVCs and alpha-site ligands act synergistically to modulate the switching of the beta-subunit from the open to the closed conformation, and this switching is crucial to the regulation of beta-site catalytic activity. Comparison of the structures of Na(+) and Cs(+) forms of the enzyme shows Cs(+) favors complexes with open indole binding sites poised for the conformational transition to the closed state, whereas the Na(+) form does not. The beta-subunits of Cs(+) complexes exhibit preformed indole subsites; the indole subsites of the open Na(+) complexes are collapsed, distorted, and too small to accommodate indole.
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Affiliation(s)
- Adam T Dierkers
- Department of Biochemistry, University of California, Riverside, California 92521, USA
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Raboni S, Bettati S, Mozzarelli A. Tryptophan synthase: a mine for enzymologists. Cell Mol Life Sci 2009; 66:2391-403. [PMID: 19387555 PMCID: PMC11115766 DOI: 10.1007/s00018-009-0028-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 03/30/2009] [Accepted: 03/31/2009] [Indexed: 01/12/2023]
Abstract
Tryptophan synthase is a pyridoxal 5'-phosphate-dependent alpha(2)beta(2) complex catalyzing the last two steps of tryptophan biosynthesis in bacteria, plants and fungi. Structural, dynamic and functional studies, carried out over more than 40 years, have unveiled that: (1) alpha- and beta-active sites are separated by about 20 A and communicate via the selective stabilization of distinct conformational states, triggered by the chemical nature of individual catalytic intermediates and by allosteric ligands; (2) indole, formed at alpha-active site, is intramolecularly channeled to the beta-active site; and (3) naturally occurring as well as genetically generated mutants have allowed to pinpoint functional and regulatory roles for several individual amino acids. These key features have made tryptophan synthase a text-book case for the understanding of the interplay between chemistry and conformational energy landscapes.
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Affiliation(s)
- Samanta Raboni
- Department of Biochemistry and Molecular Biology, University of Parma, Viale GP Usberti 23/A, 43100 Parma, Italy
- Present Address: CRIBI Biotechnology Centre, University of Padua, Padua, Italy
| | - Stefano Bettati
- Department of Biochemistry and Molecular Biology, University of Parma, Viale GP Usberti 23/A, 43100 Parma, Italy
- Italian National Institute of Biostructures and Biosystems, Parma, Italy
| | - Andrea Mozzarelli
- Department of Biochemistry and Molecular Biology, University of Parma, Viale GP Usberti 23/A, 43100 Parma, Italy
- Italian National Institute of Biostructures and Biosystems, Parma, Italy
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Barends TRM, Dunn MF, Schlichting I. Tryptophan synthase, an allosteric molecular factory. Curr Opin Chem Biol 2008; 12:593-600. [DOI: 10.1016/j.cbpa.2008.07.011] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Accepted: 07/07/2008] [Indexed: 11/25/2022]
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Dunn MF, Niks D, Ngo H, Barends TR, Schlichting I. Tryptophan synthase: the workings of a channeling nanomachine. Trends Biochem Sci 2008; 33:254-64. [DOI: 10.1016/j.tibs.2008.04.008] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Revised: 04/07/2008] [Accepted: 04/08/2008] [Indexed: 01/25/2023]
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A catalytic mechanism that explains a low catalytic activity of serine dehydratase like-1 from human cancer cells: Crystal structure and site-directed mutagenesis studies. Biochim Biophys Acta Gen Subj 2008; 1780:809-18. [DOI: 10.1016/j.bbagen.2008.01.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 01/29/2008] [Accepted: 01/30/2008] [Indexed: 11/23/2022]
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