3F6G

Crystal structure of the regulatory domain of LiCMS in complexed with isoleucine - type II

Summary for 3F6G

• Entry DOI: 10.2210/pdb3f6g/pdb
• Related: 3BLE 3BLF 3BLI 3F6H
• Descriptor: Alpha-isopropylmalate synthase, ZINC ION, ISOLEUCINE, ... (5 entities in total)
• Functional Keywords: licmsc, allosteric regulation, feedback inhibition, selectivity, specificity, transferase, acyltransferase
• Biological source: Leptospira interrogans
• Total number of polymer chains: 2
• Total formula weight: 29638.27

Authors

Zhang, P.,Ma, J.,Zhao, G.,Ding, J. (deposition date: 2008-11-06, release date: 2009-04-21, Last modification date: 2023-12-27)

Primary citation

Zhang, P.,Ma, J.,Zhang, Z.,Zha, M.,Xu, H.,Zhao, G.,Ding, J.
Molecular basis of the inhibitor selectivity and insights into the feedback inhibition mechanism of citramalate synthase from Leptospira interrogans
Biochem.J., 421:133-143, 2009

PubMed Abstract: LiCMS (Leptospira interrogans citramalate synthase) catalyses the first reaction of the isoleucine biosynthesis pathway in L. interrogans, the pathogen of leptospirosis. The catalytic reaction is regulated through feedback inhibition by its end product isoleucine. To understand the molecular basis of the high selectivity of the inhibitor and the mechanism of feedback inhibition, we determined the crystal structure of LiCMSC (C-terminal regulatory domain of LiCMS) in complex with isoleucine, and performed a biochemical study of the inhibition of LiCMS using mutagenesis and kinetic methods. LiCMSC forms a dimer of dimers in both the crystal structure and solution and the dimeric LiCMSC is the basic functional unit. LiCMSC consists of six beta-strands forming two anti-parallel beta-sheets and two alpha-helices and assumes a betaalphabeta three-layer sandwich structure. The inhibitor isoleucine is bound in a pocket at the dimer interface and has both hydrophobic and hydrogen-bonding interactions with several conserved residues of both subunits. The high selectivity of LiCMS for isoleucine over leucine is primarily dictated by the residues, Tyr430, Leu451, Tyr454, Ile458 and Val468, that form a hydrophobic pocket to accommodate the side chain of the inhibitor. The binding of isoleucine has inhibitory effects on the binding of both the substrate, pyruvate, and coenzyme, acetyl-CoA, in a typical pattern of K-type inhibition. The structural and biochemical data from the present study together suggest that the binding of isoleucine affects the binding of the substrate and coenzyme at the active site, possibly via conformational change of the dimer interface of the regulatory domain, leading to inhibition of the catalytic reaction.

PubMed: 19351325
DOI: 10.1042/BJ20090336

Experimental method

X-RAY DIFFRACTION (2 Å)