4lhc

Publication Abstract from PubMed

Glycine decarboxylase, or P-protein, is a pyridoxal 5'-phosphate (PLP) dependent enzyme in one-carbon metabolism of all organisms, in the glycine and serine catabolism of vertebrates, and in the photorespiratory pathway of oxygenic phototrophs. P-protein from the cyanobacterium Synechocystis sp. PCC 6803 is an alpha2 homodimer with high homology to eukaryotic P-proteins. The crystal structure of the apo enzyme shows the C-terminus locked in a closed conformation by a disulphide bond between Cys972 in the C-terminus and Cys353 located in the active site. Presence of the disulphide bridge isolates the active site from solvent and hinders the binding of PLP and glycine in the active site. Variants produced by substitution of Cys972 and Cys353 by Ser using site-directed mutagenesis have distinctly lower specific activities supporting the crucial role of these highly conserved redox-sensitive amino acid residues for P-protein activity. Reduction of the 353-972 disulphide releases the C-terminus and allows access to the active site. PLP and the substrate glycine bind in the active site of this reduced enzyme and appear to cause further conformational changes involving a flexible surface loop. The observation of the disulphide bond that acts to stabilise the closed form suggests a molecular mechanism for the redox-dependent activation of glycine decarboxylase observed earlier.

Structure of the Homodimeric Glycine Decarboxylase P-protein from Synechocystis sp. PCC 6803 Suggests a Mechanism for Redox-Regulation.,Hasse D, Andersson E, Carlsson G, Masloboy A, Hagemann M, Bauwe H, Andersson I J Biol Chem. 2013 Oct 11. PMID:24121504^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.