title: The three-dimensional structures of two isoforms of nucleoside diphosphate kinase from bovine retina.
abstract: The crystal structures of two isoforms of nucleoside diphosphate kinase from bovine retina overexpressed in Escherischia coli have been determined to 2.4 A resolution. Both the isoforms, NBR-A and NBR-B, are hexameric and the fold of the monomer is in agreement with NDP-kinase structures from other biological sources. Although the polypeptide chains of the two isoforms differ by only two residues, they crystallize in different space groups. NBR-A crystallizes in space group P212121 with an entire hexamer in the asymmetric unit, while NBR-B crystallizes in space group P43212 with a trimer in the asymmetric unit. The highly conserved nucleotide-binding site observed in other nucleoside diphosphate kinase structures is also observed here. Both NBR-A and NBR-B were crystallized in the presence of cGMP. The nucleotide is bound with the base in the anti conformation. The NBR-A active site contained both cGMP and GDP each bound at half occupancy. Presumably, NBR-A had retained GDP (or GTP) from the purification process. The NBR-B active site contained only cGMP.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D018360:Crystallography, X-Ray; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009701:Nucleoside-Diphosphate Kinase / Q000737:chemistry* / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D011487:Protein Conformation; D012160:Retina / Q000201:enzymology*; D012997:Solvents