Mutational Scanning of a Hairpin Loop in the Tryptophan Synthase β-Subunit Implicated in Allostery and Substrate Channeling
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Philippe Rondard
Abstract
The tryptophan synthases from Escherichia coli and Salmonella typhimurium are tetrameric enzymes, with an elongated TrpA.TrpB.TrpB.TrpA structure. Structural studies have identified residues 277–283 of TrpB as a potentially important region for the allosteric communication between the TrpA and TrpB subunits and for the transport of indole between their active sites through a hydrophobic tunnel. To explore the functional role of this region, we analyzed the effects of 19 single and double mutations in TrpB on the tryptophan synthase (TSase) and serine deaminase (SDase) activities of the TrpB2 dimer, either in the presence or in the absence of the TrpA subunit. The mutations of residues 273–283 could be divided into 4 classes. Mutations I278A, F280G and M282A decreased the SDase and TSase activities of TrpB2 to similar extents. F280A decreased the SDase activity of TrpB2 more than its TSase activity, whereas the reverse was true for Y279L. F280A decreased the activation factor of TrpB2 by TrpA, whereas F280G increased it. The reaction steps and intramolecular contacts that could be affected by the mutations are described. The sequence 278-IYFGM-282, which is present in E. coli and S. typhimurium, is only found in 5 out of 42 organisms, whereas the sequence VLHGX is found in 21 organisms. Our results identified several mutations that could be used as structural probes to analyze precisely the roles of residues 278–282 and their evolution.
Copyright © 2000 by Walter de Gruyter GmbH & Co. KG
Articles in the same Issue
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- Characterization of a Receptor for Heat Shock Protein 70 on Macrophages and Monocytes
- Yeast Translational Activator Cbs2p: Mitochondrial Targeting and Effect of Overexpression
- Mutational Scanning of a Hairpin Loop in the Tryptophan Synthase β-Subunit Implicated in Allostery and Substrate Channeling
- The Difference in the Carboxy-Terminal Sequence Is Responsible for the Difference in the Activity of Chicken and Rat Liver Fructose-2,6-Bisphosphatase
- Crystal Structure of the Caspase Activator Human Granzyme B, a Proteinase Highly Specific for an Asp-P1 Residue
- Primary Structure of Potato Kunitz-Type Serine Proteinase Inhibitor
- Activation of proPHBSP, the Zymogen of a Plasma Hyaluronan Binding Serine Protease, by an Intermolecular Autocatalytic Mechanism
- Human and Rat Dipeptidyl Peptidase III: Biochemical and Mass Spectrometric Arguments for Similarities and Differences
- Recombinant Anti-Stefin A Fab Fragment: Sequence Analysis of the Variable Region and Expression in Escherichia coli
- Green Fluorescent Protein Photobleaching: a Model for Protein Damage by Endogenous and Exogenous Singlet Oxygen
- 193 nm Photolysis of Aromatic and Aliphatic Dipeptides in Aqueous Solution: Dependence of Decomposition Quantum Yield on the Amino Acid Sequence
- NADPH:Protochlorophyllide Oxidoreductase Uses the General Import Route into Chloroplasts
- Superoxide Reactivates Nitric Oxide-Inhibited Catalase
- Erratum: The following abstract was unfortunately omitted from the GBM Fall Meeting section of the Biological Chemistry Special Supplement, Vol. 381, September 2000
- Content Index
- Author Index
- Subject Index
Articles in the same Issue
- Circadian Rhythms of Sterol 12α-Hydroxylase, Cholesterol 7α-Hydroxylase and DBP Involved in Rat Cholesterol Catabolism
- Mannosidase Action, Independent of Glucose Trimming, Is Essential for Proteasome-Mediated Degradation of Unassembled Glycosylated Ig Light Chains
- Characterization of a Receptor for Heat Shock Protein 70 on Macrophages and Monocytes
- Yeast Translational Activator Cbs2p: Mitochondrial Targeting and Effect of Overexpression
- Mutational Scanning of a Hairpin Loop in the Tryptophan Synthase β-Subunit Implicated in Allostery and Substrate Channeling
- The Difference in the Carboxy-Terminal Sequence Is Responsible for the Difference in the Activity of Chicken and Rat Liver Fructose-2,6-Bisphosphatase
- Crystal Structure of the Caspase Activator Human Granzyme B, a Proteinase Highly Specific for an Asp-P1 Residue
- Primary Structure of Potato Kunitz-Type Serine Proteinase Inhibitor
- Activation of proPHBSP, the Zymogen of a Plasma Hyaluronan Binding Serine Protease, by an Intermolecular Autocatalytic Mechanism
- Human and Rat Dipeptidyl Peptidase III: Biochemical and Mass Spectrometric Arguments for Similarities and Differences
- Recombinant Anti-Stefin A Fab Fragment: Sequence Analysis of the Variable Region and Expression in Escherichia coli
- Green Fluorescent Protein Photobleaching: a Model for Protein Damage by Endogenous and Exogenous Singlet Oxygen
- 193 nm Photolysis of Aromatic and Aliphatic Dipeptides in Aqueous Solution: Dependence of Decomposition Quantum Yield on the Amino Acid Sequence
- NADPH:Protochlorophyllide Oxidoreductase Uses the General Import Route into Chloroplasts
- Superoxide Reactivates Nitric Oxide-Inhibited Catalase
- Erratum: The following abstract was unfortunately omitted from the GBM Fall Meeting section of the Biological Chemistry Special Supplement, Vol. 381, September 2000
- Content Index
- Author Index
- Subject Index
