title: Structural studies of glucose-6-phosphate and NADP+ binding to human glucose-6-phosphate dehydrogenase.
abstract: Human glucose-6-phosphate dehydrogenase (G6PD) is NADP(+)-dependent and catalyses the first and rate-limiting step of the pentose phosphate shunt. Binary complexes of the human deletion mutant, DeltaG6PD, with glucose-6-phosphate and NADP(+) have been crystallized and their structures solved to 2.9 and 2.5 A, respectively. The structures are compared with the previously determined structure of the Canton variant of human G6PD (G6PD(Canton)) in which NADP(+) is bound at the structural site. Substrate binding in DeltaG6PD is shown to be very similar to that described previously in Leuconostoc mesenteroides G6PD. NADP(+) binding at the coenzyme site is seen to be comparable to NADP(+) binding in L. mesenteroides G6PD, although some differences arise as a result of sequence changes. The tetramer interface varies slightly among the human G6PD complexes, suggesting flexibility in the predominantly hydrophilic dimer-dimer interactions. In both complexes, Pro172 of the conserved peptide EKPxG is in the cis conformation; it is seen to be crucial for close approach of the substrate and coenzyme during the enzymatic reaction. Structural NADP(+) binds in a very similar way in the DeltaG6PD-NADP(+) complex and in G6PD(Canton), while in the substrate complex the structural NADP(+) has low occupancy and the C-terminal tail at the structural NADP(+) site is disordered. The implications of possible interaction between the structural NADP(+) and G6P are considered.
authors.affiliation: Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, England. masayo.kotaka@strubi.ox.ac.uk
authors.forename: Masayo
authors.initials: M
authors.lastname: Kotaka
authors.forename: Sheila
authors.initials: S
authors.lastname: Gover
authors.forename: Lucy
authors.initials: L
authors.lastname: Vandeputte-Rutten
authors.forename: Shannon W N
authors.initials: SW
authors.lastname: Au
authors.forename: Veronica M S
authors.initials: VM
authors.lastname: Lam
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Adams
mesh_terms: D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D003627:Data Interpretation, Statistical; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D019298:Glucose-6-Phosphate / Q000737:chemistry / Q000378:metabolism*; D005954:Glucosephosphate Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation / Q000502:physiology; D009249:NADP / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D009249:NADP; D019298:Glucose-6-Phosphate; D005954:Glucosephosphate Dehydrogenase