1
|
Takashima M, Watanabe I, Miyanaga A, Eguchi T. Substrate specificity of Chondroitinase ABC I based on analyses of biochemical reactions and crystal structures in complex with disaccharides. Glycobiology 2021; 31:1571-1581. [PMID: 34392362 PMCID: PMC8684500 DOI: 10.1093/glycob/cwab086] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 08/05/2021] [Accepted: 08/05/2021] [Indexed: 11/28/2022] Open
Abstract
Chondroitinase ABC I (cABC-I) is the enzyme which cleaves the β-1,4 glycosidic linkage of chondroitin sulfate (CS) by β-elimination. To elucidate more accurately the substrate specificity of cABC-I, we evaluated the kinetic parameters of cABC-I and its reactivity with CS isomers displaying less structural heterogeneity as substrates, e.g., approximately 90 percent of disaccharide units in Chondroitin sulfate A (CSA) or Chondroitin sulfate C (CSC) is D-glucuronic acid and 4-O-sulfated N-acetyl galactosamine (GalNAc) (A-unit) or D-glucuronic acid and 6-O-sulfated GalNAc (C-unit), respectively. cABC-I showed the highest reactivity to CSA and CSC among all CS isomers, and the kcat/Km of cABC-I was higher for CSA than for CSC. Next, we determined the crystal structures of cABC-I in complex with CS disaccharides, and analyzed the crystallographic data in combination with molecular docking data. Arg500 interacts with 4-O-sulfated and 6-O-sulfated GalNAc residues. The distance between Arg500 and the 4-O-sulfate group was 0.8 Å shorter than that between Arg500 and the 6-O-sulfated group. Moreover, it is likely that the 6-O-sulfated group is electrostatically repulsed by the nearby Asp490. Thus, we demonstrated that cABC-I has the highest affinity for the CSA richest in 4-O-sulfated GalNAc residues among all CS isomers. Recently, cABC-I was used to treat lumbar disc herniation. The results provide useful information to understand the mechanism of the pharmacological action of cABC-I.
Collapse
Affiliation(s)
- Makoto Takashima
- Department of Chemistry, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Ippei Watanabe
- Medical Affairs, Seikagaku Corporation, 1-6-1 Marunouchi, Chiyoda-ku, Tokyo 100-0005, Japan
| | - Akimasa Miyanaga
- Department of Chemistry, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Tadashi Eguchi
- Department of Chemistry, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan
| |
Collapse
|
2
|
Domanska A, Guryanov S, Butcher SJ. A comparative analysis of parechovirus protein structures with other picornaviruses. Open Biol 2021; 11:210008. [PMID: 34315275 PMCID: PMC8316810 DOI: 10.1098/rsob.210008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Parechoviruses belong to the genus Parechovirus within the family Picornaviridae and are non-enveloped icosahedral viruses with a single-stranded RNA genome. Parechoviruses include human and animal pathogens classified into six species. Those that infect humans belong to the Parechovirus A species and can cause infections ranging from mild gastrointestinal or respiratory illness to severe neonatal sepsis. There are no approved antivirals available to treat parechovirus (nor any other picornavirus) infections. In this parechovirus review, we focus on the cleaved protein products resulting from the polyprotein processing after translation comparing and contrasting their known or predicted structures and functions to those of other picornaviruses. The review also includes our original analysis from sequence and structure prediction. This review highlights significant structural differences between parechoviral and other picornaviral proteins, suggesting that parechovirus drug development should specifically be directed to parechoviral targets.
Collapse
Affiliation(s)
- Aušra Domanska
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Bioscience Research Programme, and Helsinki Institute of Life Sciences-Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland
| | - Sergey Guryanov
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Bioscience Research Programme, and Helsinki Institute of Life Sciences-Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland
| | - Sarah J Butcher
- Faculty of Biological and Environmental Sciences, Molecular and Integrative Bioscience Research Programme, and Helsinki Institute of Life Sciences-Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland
| |
Collapse
|
3
|
Abstract
Bioorthogonal, chemoselective ligation methods are an essential part of the tools utilized to investigate biochemical pathways. Specifically enzymatic approaches are valuable methods in this context due to the inherent specificity of the deployed enzymes and the mild conditions of the modification reactions. One of the most common strategies is based on the transpeptidation catalyzed by sortase A derived from Staphylococcus aureus. The procedure is well established and a wide variety of applications have been published to date. Here, implementations of sortase A, which range from protein labeling using fluorescence dyes and the preparation of cyclic proteins to the modification of entire cells, are summarized. Furthermore, there is a focus on the optimization approaches established to solve the drawbacks of sortase-mediated transpeptidation.
Collapse
Affiliation(s)
- Markus Ritzefeld
- Bielefeld University, Department of Chemistry, Organic and Bioorganic Chemistry (OCIII), Universitätsstrasse 25, 33615 Bielefeld (Germany).
| |
Collapse
|
4
|
Shokhen M, Hirsch M, Khazanov N, Ozeri R, Perlman N, Traube T, Vijayakumar S, Albeck A. From Catalytic Mechanism to Rational Design of Reversible Covalent Inhibitors of Serine and Cysteine Hydrolases. Isr J Chem 2014. [DOI: 10.1002/ijch.201300144] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
5
|
Villamil MA, Chen J, Liang Q, Zhuang Z. A Noncanonical Cysteine Protease USP1 Is Activated through Active Site Modulation by USP1-Associated Factor 1. Biochemistry 2012; 51:2829-39. [DOI: 10.1021/bi3000512] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mark A. Villamil
- Department
of Chemistry and Biochemistry, 214A Drake
Hall, University of Delaware, Newark, Delaware
19716, United States
| | - Junjun Chen
- Department
of Chemistry and Biochemistry, 214A Drake
Hall, University of Delaware, Newark, Delaware
19716, United States
| | - Qin Liang
- Department
of Chemistry and Biochemistry, 214A Drake
Hall, University of Delaware, Newark, Delaware
19716, United States
| | - Zhihao Zhuang
- Department
of Chemistry and Biochemistry, 214A Drake
Hall, University of Delaware, Newark, Delaware
19716, United States
| |
Collapse
|
6
|
Gouvea IE, Santos JAN, Burlandy FM, Tersariol ILS, da Silva EE, Juliano MA, Juliano L, Cunha RLOR. Poliovirus 3C proteinase inhibition by organotelluranes. Biol Chem 2011; 392:587-91. [PMID: 21521074 DOI: 10.1515/bc.2011.059] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
The 3C proteinase, essential for human poliovirus (PV) replication, has unique characteristics as its three-dimensional structure resembles chymotrypsin, but its catalytic nucleophile is a cysteine SH group rather than the OH group of serine. Here, we describe the use of tellurium compounds as inhibitors of PV3C proteinase. A rapid, stoichiometric and covalent inactivation of PV3C was observed with both a chloro-telluroxetane and a bis-vinylic organotellurane. These compounds also inhibit human cathepsins B, L, S, and K with second order rate constants higher than those obtained for PV3C. Chloro-telluroxetane inhibits replication of PV in human embryonic rhabdomyosarcoma cells in the low micromolar range and below the toxic level for the host cells. Bis-vinylic organotellurane is more effective as antiviral agent but reduces the cell viability by 20% at 10 μm, a concentration almost completely inhibiting virus growth. This is the first description of inhibition of viral 3C proteinase with antiviral property by this class of compounds.
Collapse
Affiliation(s)
- Iuri E Gouvea
- Departamento de Biofísica, Escola Paulista de Medicina, Universidade Federal de São Paulo, Rua Três de Maio,100, São Paulo, SP 04044-020, Brazil
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Shokhen M, Khazanov N, Albeck A. The mechanism of papain inhibition by peptidyl aldehydes. Proteins 2010; 79:975-85. [DOI: 10.1002/prot.22939] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 10/31/2010] [Accepted: 11/02/2010] [Indexed: 01/27/2023]
|
8
|
Okamoto DN, Oliveira LC, Kondo MY, Cezari MH, Szeltner Z, Juhász T, Juliano MA, Polgár L, Juliano L, Gouvea IE. Increase of SARS-CoV 3CL peptidase activity due to macromolecular crowding effects in the milieu composition. Biol Chem 2010; 391:1461-8. [DOI: 10.1515/bc.2010.145] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The 3C-like peptidase of the severe acute respiratory syndrome virus (SARS-CoV) is strictly required for viral replication, thus being a potential target for the development of antiviral agents. In contrast to monomeric picornavirus 3C peptidases, SARS-CoV 3CLpro exists in equilibrium between the monomer and dimer forms in solution, and only the dimer is proteolytically active in dilute buffer solutions. In this study, the increase of SARS-CoV 3CLpro peptidase activity in presence of kosmotropic salts and crowding agents is described. The activation followed the Hofmeister series of anions, with two orders of magnitude enhancement in the presence of Na2SO4, whereas the crowding agents polyethylene glycol and bovine serum albumin increased the hydrolytic rate up to 3 times. Kinetic determinations of the monomer dimer dissociation constant (K
d) indicated that activation was a result of a more active dimer, without significant changes in K
d values. The activation was found to be independent of substrate length and was derived from both k
cat increase and K
m decrease. The viral peptidase activation described here could be related to the crowded intracellular environment and indicates a further fine-tuning mechanism for biological control, particularly in the microenvironment of the vesicles that are induced in host cells during positive strand RNA virus infection.
Collapse
|
9
|
Shokhen M, Khazanov N, Albeck A. Challenging a paradigm: theoretical calculations of the protonation state of the Cys25-His159 catalytic diad in free papain. Proteins 2010; 77:916-26. [PMID: 19688822 DOI: 10.1002/prot.22516] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A central mechanistic paradigm of cysteine proteases is that the His-Cys catalytic diad forms an ion-pair NH(+)/S(-) already in the catalytically active free enzyme. Most molecular modeling studies of cysteine proteases refer to this paradigm as their starting point. Nevertheless, several recent kinetics and X-ray crystallography studies of viral and bacterial cysteine proteases depart from the ion-pair mechanism, suggesting general base catalysis. We challenge the postulate of the ion-pair formation in free papain. Applying our QM/SCRF(VS) molecular modeling approach, we analyzed all protonation states of the catalytic diad in free papain and its SMe derivative, comparing the predicted and experimental pK(a) data. We conclude that the His-Cys catalytic diad in free papain is fully protonated, NH(+)/SH. The experimental pK(a) = 8.62 of His159 imidazole in free papain, obtained by NMR-controlled titration and originally interpreted as the NH(+)/S(-) <==> N/S(-) NH(+)/S(-) <==> N/S(-) equilibrium, is now assigned to the NH(+)/SH <==> N/SH NH(+)/SH <==> N/SH equilibrium.
Collapse
Affiliation(s)
- Michael Shokhen
- Department of Chemistry, The Julius Spokojny Bioorganic Chemistry Laboratory, Bar Ilan University, Ramat Gan 52900, Israel.
| | | | | |
Collapse
|
10
|
Sejwal P, Narasimhan SK, Prashar D, Bandyopadhyay D, Luk YY. Selective Immobilization of Peptides Exclusively via N-Terminus Cysteines by Water-Driven Reactions on Surfaces. J Org Chem 2009; 74:6843-6. [DOI: 10.1021/jo901085u] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Preeti Sejwal
- Department of Chemistry, Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York 13244
| | - Sri Kamesh Narasimhan
- Department of Chemistry, Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York 13244
| | - Deepali Prashar
- Department of Chemistry, Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York 13244
| | - Debjyoti Bandyopadhyay
- Department of Chemistry, Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York 13244
| | - Yan-Yeung Luk
- Department of Chemistry, Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York 13244
| |
Collapse
|
11
|
Nelson KJ, Parsonage D, Hall A, Karplus PA, Poole LB. Cysteine pK(a) values for the bacterial peroxiredoxin AhpC. Biochemistry 2008; 47:12860-8. [PMID: 18986167 PMCID: PMC2645924 DOI: 10.1021/bi801718d] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Salmonella typhimurium AhpC is a founding member of the peroxiredoxin family, a ubiquitous group of cysteine-based peroxidases with high reactivity toward hydrogen peroxide, organic hydroperoxides, and peroxynitrite. For all of the peroxiredoxins, the catalytic cysteine, referred to as the peroxidatic cysteine (C(P)), acts as a nucleophile in attacking the peroxide substrate, forming a cysteine sulfenic acid at the active site. Because thiolates are far stronger nucleophiles than thiol groups, it is generally accepted that cysteine-based peroxidases should exhibit pK(a) values lower than an unperturbed value of 8.3-8.5. In this investigation, several independent approaches were used to assess the pK(a) of the two cysteinyl residues of AhpC. Methods using two different iodoacetamide derivatives yielded unperturbed pK(a) values (7.9-8.7) for both cysteines, apparently due to reactivity with the wrong conformation of C(P) (i.e., locally unfolded and flipped out of the active site), as supported by X-ray crystallographic analyses. A functional pK(a) of 5.94 +/- 0.10 presumably reflecting the titration of C(P) within the fully folded active site was obtained by measuring AhpC competition with horseradish peroxidase for hydrogen peroxide; this value is quite similar to that obtained by analyzing the pH dependence of the epsilon(240) of wild-type AhpC (5.84 +/- 0.02) and similar to those obtained for two typical 2-cysteine peroxiredoxins from Saccharomyces cerevisiae (5.4 and 6.0). Thus, the pK(a) value of AhpC balances the need for a deprotonated thiol (at pH 7, approximately 90% of the C(P) would be deprotonated) with the fact that thiolates with higher pK(a) values are stronger nucleophiles.
Collapse
Affiliation(s)
- Kimberly J. Nelson
- Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157
| | - Derek Parsonage
- Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157
| | - Andrea Hall
- Department of Biochemistry and Biophysics, Oregon State University, 2011 Ag Life Sciences Building, Corvallis, Oregon 97331
| | - P. Andrew Karplus
- Department of Biochemistry and Biophysics, Oregon State University, 2011 Ag Life Sciences Building, Corvallis, Oregon 97331
| | - Leslie B. Poole
- Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157
| |
Collapse
|
12
|
Someya Y, Takeda N, Wakita T. Saturation mutagenesis reveals that GLU54 of norovirus 3C-like protease is not essential for the proteolytic activity. J Biochem 2008; 144:771-80. [PMID: 18838436 PMCID: PMC7109903 DOI: 10.1093/jb/mvn130] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Accepted: 09/22/2008] [Indexed: 11/13/2022] Open
Abstract
The norovirus 3C-like protease is a member of the chymotrypsin-like serine protease superfamily. Previous characterization of its crystal structure has implicated the Glu54-His30-Cys139 triad in the catalysis. In the present study, the Glu54 residue of the protease was subjected to site-saturation mutagenesis, with the result that nearly half of the mutants retained the significant proteolytic activity. It was suggested that a carboxylate at position 54 was not essential for the activity. The in vitro assays of the proteolysis revealed that most of Glu54 mutants retained relatively high proteolytic activity. When the Glu54 mutation was combined with the Ser mutation of the Cys139 residue, a nucleophile, only the Asp54 and Gln54 mutations showed proteolytic activity comparable to that of the Ser139 single mutant, suggesting that a hydrogen bond between Glu54 and His30 was critical in the Ser139 background. These results suggested that the mechanism of the proteolysis by the wild-type norovirus 3C-like protease was different from that of typical chymotrypsin-like serine proteases.
Collapse
Affiliation(s)
- Yuichi Someya
- Department of Virology II, National Institute of Infectious Diseases, Musashi-Murayama, Tokyo 208-0011, Japan.
| | | | | |
Collapse
|
13
|
Li L, Li Z, Wang C, Xu D, Mariano PS, Guo H, Dunaway-Mariano D. The Electrostatic Driving Force for Nucleophilic Catalysis in l-Arginine Deiminase: A Combined Experimental and Theoretical Study. Biochemistry 2008; 47:4721-32. [DOI: 10.1021/bi7023496] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ling Li
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131
| | - Zhimin Li
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131
| | - Canhui Wang
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131
| | - Dingguo Xu
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131
| | - Patrick S. Mariano
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131
| | - Debra Dunaway-Mariano
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131
| |
Collapse
|
14
|
Curry S, Roqué-Rosell N, Sweeney TR, Zunszain PA, Leatherbarrow RJ. Structural analysis of foot-and-mouth disease virus 3C protease: a viable target for antiviral drugs? Biochem Soc Trans 2007; 35:594-8. [PMID: 17511659 DOI: 10.1042/bst0350594] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Foot-and-mouth disease virus causes a major global agricultural problem that is difficult to control with existing vaccines. Structural analyses of the viral 3C protease not only have provided fresh insights into the catalytic mechanism of an unusual class of chymotrypsin-like cysteine proteases, but also are generating valuable information to drive the quest for effective antiviral therapies.
Collapse
Affiliation(s)
- S Curry
- Biophysics Section, Division of Cell and Molecular Biology, Blackett Laboratory, Imperial College, Exhibition Road, London SW7 2AZ, UK.
| | | | | | | | | |
Collapse
|
15
|
Curry S, Roqué-Rosell N, Zunszain PA, Leatherbarrow RJ. Foot-and-mouth disease virus 3C protease: recent structural and functional insights into an antiviral target. Int J Biochem Cell Biol 2006; 39:1-6. [PMID: 16979372 PMCID: PMC7185863 DOI: 10.1016/j.biocel.2006.07.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Revised: 07/25/2006] [Accepted: 07/26/2006] [Indexed: 02/05/2023]
Abstract
The 3C protease from foot-and-mouth disease virus (FMDV 3C(pro)) is critical for viral pathogenesis, having vital roles in both the processing of the polyprotein precursor and RNA replication. Although recent structural and functional studies have revealed new insights into the mechanism and function of the enzyme, key questions remain that must be addressed before the potential of FMDV 3C(pro) as an antiviral drug target can be realised.
Collapse
Affiliation(s)
- Stephen Curry
- Biophysics Section, Division of Cell and Molecular Biology, Blackett Laboratory, Imperial College, Exhibition Road, London SW7 2AZ, UK.
| | | | | | | |
Collapse
|
16
|
Connolly KM, Smith BT, Pilpa R, Ilangovan U, Jung ME, Clubb RT. Sortase from Staphylococcus aureus does not contain a thiolate-imidazolium ion pair in its active site. J Biol Chem 2003; 278:34061-5. [PMID: 12824164 DOI: 10.1074/jbc.m305245200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Many surface proteins are anchored to the cell wall by the action of sortase enzymes, a recently discovered family of cysteine transpeptidases. As the surface proteins of human pathogens are frequently required for virulence, the sortase-mediated anchoring reaction represents a potential target for new anti-infective agents. It has been suggested that the sortase from Staphylococcus aureus (SrtA), may use a similar catalytic strategy as the papain cysteine proteases, holding its Cys184 side chain in an active configuration through a thiolate-imidazolium ion interaction with residue His120. To investigate the mechanism of transpeptidation, we have synthesized a peptidyl-vinyl sulfone substrate mimic that irreversibly inhibits SrtA. Through the study of the pH dependence of SrtA inhibition and NMR, we have estimated the pKas of the active site thiol (Cys184) and imidazole (His120) to be approximately 9.4 and 7.0, respectively. These measurements are inconsistent with the existence of a thiolate-imidazolium ion pair and suggest a general base catalysis mechanism during transpeptidation.
Collapse
Affiliation(s)
- Kevin M Connolly
- Department of Chemistry and Biochemistry, Molecular Biology Institute and UCLA-Department of Energy Institute for Genomics and Proteomics, UCLA, Los Angeles, California 90095-1570, USA
| | | | | | | | | | | |
Collapse
|