Download MendeleyCrystallographic Structures of IlvN·Val/Ile Complexes: Conformational Selectivity for Feedback Inhibition of Aceto Hydroxy Acid Synthases.
Bansal, A., Karanth, N.M., Demeler, B., Schindelin, H., Sarma, S.P.(2019) Biochemistry 58: 1992-2008
- PubMed: 30887800
- DOI: https://doi.org/10.1021/acs.biochem.9b00050
- Primary Citation of Related Structures:
5YPP, 5YPW, 5YPY, 5YUM - PubMed Abstract:
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 Å) 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 Cys 43 is 2-fold disordered (χ 1 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 His 53 , located at the surface of the protein, exhibits two conformations in the IlvN·Val complex. The concerted conformational switch in the side chains of Cys 43 and His 53 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.
Organizational Affiliation:
Molecular Biophysics Unit , Indian Institute of Science , Bangalore , Karnataka 560012 , India.
