A conserved surface loop in type I dehydroquinate dehydratases positions an active site arginine and functions in substrate binding.

ABSTRACT: Dehydroquinate dehydratase (DHQD) catalyzes the third step in the biosynthetic shikimate pathway. We present three crystal structures of the Salmonella enterica type I DHQD that address the functionality of a surface loop that is observed to close over the active site following substrate binding. Two wild-type structures with differing loop conformations and kinetic and structural studies of a mutant provide evidence of both direct and indirect mechanisms of involvement of the loop in substrate binding. In addition to allowing amino acid side chains to establish a direct interaction with the substrate, closure of the loop necessitates a conformational change of a key active site arginine, which in turn positions the substrate productively. The absence of DHQD in humans and its essentiality

SUBMITTER: Light SH 

PROVIDER: S-EPMC3062685 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature