title: Ligand-induced conformational changes and a mechanism for domain closure in Aspergillus nidulans dehydroquinate synthase.
abstract: In order to investigate systematically substrate and cofactor-induced conformational changes in the enzyme dehydroquinate synthase (DHQS), eight structures representing a series of differently liganded states have been determined in a total of six crystal forms. DHQS in the absence of the substrate analogue carbaphosphonate, either unliganded or in the presence of NAD or ADP, is in an open form where a relative rotation of 11-13 degrees between N and C-terminal domains occurs. Analysis of torsion angle difference plots between sets of structures reveals eight rearrangements that appear relevant to domain closure and a further six related to crystal packing. Overlapping 21 different copies of the individual N and C-terminal DHQS domains further reveals a series of pivot points about which these movements occur and illustrates the way in which widely separated secondary structure elements are mechanically inter-linked to form "composite elements", which propagate structural changes across large distances. This analysis has provided insight into the basis of DHQS ligand-initiated domain closure and gives rise to the proposal of an ordered sequence of events involving substrate binding, and local rearrangements within the active site that are propagated to the hinge regions, leading to closure of the active-site cleft.
authors.affiliation: Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK.
authors.forename: C E
authors.initials: CE
authors.lastname: Nichols
authors.forename: J
authors.initials: J
authors.lastname: Ren
authors.forename: H K
authors.initials: HK
authors.lastname: Lamb
authors.forename: A R
authors.initials: AR
authors.lastname: Hawkins
authors.forename: D K
authors.initials: DK
authors.lastname: Stammers
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology*; D001233:Aspergillus nidulans / Q000201:enzymology*; D018360:Crystallography, X-Ray; D008024:Ligands; D008958:Models, Molecular; D009243:NAD / Q000494:pharmacology*; D063065:Organophosphonates / Q000494:pharmacology*; D019761:Phosphorus-Oxygen Lyases / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000187:drug effects; D012997:Solvents; D055672:Static Electricity; D013379:Substrate Specificity
chemical_list: D008024:Ligands; D063065:Organophosphonates; D012997:Solvents; D009243:NAD; D000244:Adenosine Diphosphate; C020001:3-dehydroquinate synthetase; D019761:Phosphorus-Oxygen Lyases