1hpc
REFINED STRUCTURES AT 2 ANGSTROMS AND 2.2 ANGSTROMS OF THE TWO FORMS OF THE H-PROTEIN, A LIPOAMIDE-CONTAINING PROTEIN OF THE GLYCINE DECARBOXYLASE
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OverviewOverview
H-protein, a 14 kDa lipoic acid-containing protein is a component of the, glycine decarboxylase complex. This complex which consists of four protein, components (P-, H-, T- and L-protein) catalyzes the oxidative, decarboxylation of glycine. The mechanistic heart of the complex is, provided by the lipoic acid attached to a lysine residue of the H-protein., It undergoes a cycle of transformations, i.e. reductive methylamination, methylamine transfer, and electron transfer. We present details of the, crystal structures of the H-protein, in its two forms, H-Pro(Ox) with, oxidized lipoamide and H-Pro(Met) with methylamine-loaded lipoamide. X-ray, diffraction data were collected from crystals of H-Pro(Ox) to 2 and, H-Pro(Met) to 2.2 A resolution. The final R-factor value for the H-Pro(Ox), is 18.5% for data with F > 2sigma. in the range of 8.0-2.0 A resolution., The refinement confirmed our previous model, refined to 2.6 A, of a, beta-fold sandwich structure with two beta-sheets. The lipoamide arm, attached to Lys63, located in the loop of a hairpin conformation, is, clearly visible at the surface of the protein. The H-Pro(Met) has been, crystallized in orthorhombic and monoclinic forms and the structures were, solved by molecular replacement, starting from the H-Pro(Ox) model. The, orthorhombic structure has been refined with a final R-factor value of, 18.5% for data with F > 2sigma in the range of 8.0-2.2 A resolution. The, structure of the monoclinic form has been refined with a final R-factor, value of 17.5% for data with F > 2sigma in the range of 15.0-3.0 A. In, these two structures which have similar packing, the protein conformation, is identical to the conformation found in the H-Pro(Ox). The main change, lies in the position of the lipoamide group which has moved significantly, when loaded with methylamine. In this case the methylamine-lipoamide group, is tucked into a cleft at the surface of the protein where it is, stabilized by hydrogen bonds and hydrophobic contacts. Thus, it is totally, protected and not free to move in aqueous solvent. In addition, the, H-protein presents some sequence and structural analogies with other, lipoate- and biotin-containing proteins and also with proteins of the, phosphoenolpyruvate:sugar phosphotransferase system.
About this StructureAbout this Structure
1HPC is a Single protein structure of sequence from Pisum sativum with LPA as ligand. Active as Glycine dehydrogenase (decarboxylating), with EC number 1.4.4.2 Full crystallographic information is available from OCA.
ReferenceReference
Refined structures at 2 and 2.2 A resolution of two forms of the H-protein, a lipoamide-containing protein of the glycine decarboxylase complex., Pares S, Cohen-Addad C, Sieker LC, Neuburger M, Douce R, Acta Crystallogr D Biol Crystallogr. 1995 Nov 1;51(Pt 6):1041-51. PMID:15299773
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