The slow-onset nature of allosteric inhibition in α-isopropylmalate synthase from Mycobacterium tuberculosis is mediated by a flexible loop.
The identification of structure-function relationships in allosteric enzymes is essential to describing a molecular mechanism for allosteric processes. The enzyme α-isopropylmalate synthase from Mycobacterium tuberculosis (MtIPMS) is subject to slow-onset, allosteric inhibition by l-leucine. Here we report that alternate amino acids act as rapid equilibrium noncompetitive inhibitors of MtIPMS failing to display biphasic inhibition kinetics. Amino acid substitutions on a flexible loop covering the regulatory binding pocket generate enzyme variants that have significant affinity for l-leucine but lack biphasic inhibition kinetics. Taken together, these results are consistent with the flexible loop mediating the slow-onset step of allosteric inhibition.
Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487, USA.
Ashley K
AK
Casey
Joshua
J
Baugh
Patrick A
PA
Frantom
D015079:2-Isopropylmalate Synthase / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000494:Allosteric Regulation; D020134:Catalytic Domain; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000201:enzymology*
D015079:2-Isopropylmalate Synthase