2id2
From Proteopedia
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GAPN T244S mutant X-ray structure at 2.5 A
Overview
One of the most striking features of several X-ray structures of, CoA-independent ALDHs (aldehyde dehydrogenases) in complex with NAD(P) is, the conformational flexibility of the NMN moiety. However, the fact that, the rate of the acylation step is high in GAPN (non-phosphorylating, glyceraldehyde-3-phosphate dehydrogenase) from Streptococcus mutans, implies an optimal positioning of the nicotinamide ring relative to the, hemithioacetal intermediate within the ternary GAPN complex to allow an, efficient and stereospecific hydride transfer. Substitutions of serine for, invariant Thr244 and alanine for Lys178 result in a drastic decrease of, the efficiency of hydride transfer which becomes rate-limiting. The, crystal structure of the binary complex T244S GAPN-NADP shows that the, absence of the beta-methyl group leads to a well-defined conformation of, the NMN part, including the nicotinamide ring, clearly different from that, depicted to be suitable for an efficient hydride transfer in the, wild-type. The approximately 0.6-unit increase in pK(app) of the catalytic, Cys302 observed in the ternary complex for both mutated GAPNs is likely to, be due to a slight difference in positioning of the nicotinamide ring, relative to Cys302 with respect to the wild-type ternary complex. Taken, together, the data support a critical role of the Thr244 beta-methyl, group, held in position through a hydrogen-bond interaction between the, Thr244 beta-hydroxy group and the epsilon-amino group of Lys178, in, permitting the nicotinamide ring to adopt a conformation suitable for an, efficient hydride transfer during the acylation step for all the members, of the CoA-independent ALDH family.
About this Structure
2ID2 is a Single protein structure of sequence from Streptococcus mutans with and as ligands. Active as Glyceraldehyde-3-phosphate dehydrogenase (NADP(+)), with EC number 1.2.1.9 Full crystallographic information is available from OCA.
Reference
Invariant Thr244 is essential for the efficient acylation step of the non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase from Streptococcus mutans., Pailot A, D'Ambrosio K, Corbier C, Talfournier F, Branlant G, Biochem J. 2006 Dec 15;400(3):521-30. PMID:16958622
Page seeded by OCA on Wed Jan 23 13:33:44 2008
