Crystal structure of tetrameric homoisocitrate dehydrogenase from an extreme thermophile, Thermus thermophilus: involvement of hydrophobic dimer-dimer interaction in extremely high thermotolerance.

ABSTRACT: The crystal structure of homoisocitrate dehydrogenase involved in lysine biosynthesis from Thermus thermophilus (TtHICDH) was determined at 1.85-A resolution. Arg85, which was shown to be a determinant for substrate specificity in our previous study, is positioned close to the putative substrate binding site and interacts with Glu122. Glu122 is highly conserved in the equivalent position in the primary sequence of ICDH and archaeal 3-isopropylmalate dehydrogenase (IPMDH) but interacts with main- and side-chain atoms in the same domain in those paralogs. In addition, a conserved Tyr residue (Tyr125 in TtHICDH) which extends its side chain toward a substrate and thus has a catalytic function in the related beta-decarboxylating dehydrogenases, is flipped out of the substrate-binding site. The

SUBMITTER: Miyazaki J 

PROVIDER: S-EPMC1251591 | biostudies-literature | 2005 Oct

REPOSITORIES: biostudies-literature