title: 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 in many pathogenic bacteria make the enzyme a target for the development of nontoxic antimicrobials. The structures and ligand binding insights presented here may inform the design of novel type I DHQD inhibiting molecules.
authors.affiliation: Center for Structural Genomics of Infectious Diseases, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, United States.
authors.forename: Samuel H
authors.initials: SH
authors.lastname: Light
authors.forename: George
authors.initials: G
authors.lastname: Minasov
authors.forename: Ludmilla
authors.initials: L
authors.lastname: Shuvalova
authors.forename: Scott N
authors.initials: SN
authors.lastname: Peterson
authors.forename: Michael
authors.initials: M
authors.lastname: Caffrey
authors.forename: Wayne F
authors.initials: WF
authors.lastname: Anderson
authors.forename: Arnon
authors.initials: A
authors.lastname: Lavie
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine; D055162:Biocatalysis; D020134:Catalytic Domain; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D006836:Hydro-Lyases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D019779:Salmonella enterica / Q000201:enzymology*
chemical_list: D001120:Arginine; D006836:Hydro-Lyases; C020000:3-dehydroquinate dehydratase