Crystallographic Structures of IlvN·Val/Ile Complexes: Conformational Selectivity for Feedback Inhibition of Aceto Hydroxy Acid Synthases
| Autor: | Hermann Schindelin, Borries Demeler, N. Megha Karanth, Akanksha Bansal, Siddhartha P. Sarma |
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| Rok vydání: | 2019 |
| Předmět: |
Models
Molecular Protein Conformation Dimer Protein subunit Crystallography X-Ray Biochemistry Article chemistry.chemical_compound Protein structure Valine Side chain Transferase Amino Acid Sequence Isoleucine Feedback Physiological chemistry.chemical_classification Binding Sites Escherichia coli Proteins Hydrogen Bonding Amino acid Acetolactate Synthase Crystallography chemistry Protein Binding |
| Zdroj: | Biochemistry. 58:1992-2008 |
| ISSN: | 1520-4995 0006-2960 |
| Popis: | Conformational factors that predicate selectivity for valine or isoleucine binding to IlvN leading to the regulation of aceto hydroxy acid synthase I (AHAS I) of Escherichia coli have been determined for the first time from high-resolution (1.9-2.43 A) crystal structures of IlvN·Val and IlvN·Ile complexes. The valine and isoleucine ligand binding pockets are located at the dimer interface. In the IlvN·Ile complex, among residues in the binding pocket, the side chain of Cys43 is 2-fold disordered (χ1 angles of gauche- and trans). Only one conformation can be observed for the identical residue in the IlvN·Val complexes. In a reversal, the side chain of His53, located at the surface of the protein, exhibits two conformations in the IlvN·Val complex. The concerted conformational switch in the side chains of Cys43 and His53 may play an important role in the regulation of the AHAS I holoenzyme activity. A significant result is the establishment of the subunit composition in the AHAS I holoenzyme by analytical ultracentrifugation. Solution nuclear magnetic resonance and analytical ultracentrifugation experiments have also provided important insights into the hydrodynamic properties of IlvN in the ligand-free and -bound states. The structural and biophysical data unequivocally establish the molecular basis for differential binding of the ligands to IlvN and a rationale for the resistance of IlvM to feedback inhibition by the branched-chain amino acids. |
| Databáze: | OpenAIRE |
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