Abstract
Crystal Structure of Nucleosie Diphosphate Kinase in Rice Nucleoside diphosphate kinase (NDK) is a ubiquitous enzyme found in all organisms (eukaryotes and prokaryotes) and cell type. It catalyses the transfer of the tpphosphoryl group from a nucleoside triphosphate (NTP) to a nucleoside diphosphate (NDP). NDK is involved and required for coleoptile elongation in rice. The level of the enzyme changes during seed germination and the early stages of seedling growth. Although several NDK structures from bacteria and animals have previously been available, the structures from plants are not yet determined.Crystals of the rice NDK have been obtained and several sets of data were collected at SPring-8 BL12B2 in Japan. The crystals belong to the space group P2(1)2(1)2(1) with unit-cell parameters a = 70.98 A, b = 182.26 A, c = 188.30 A, and diffract to 2.5 A. The structure is determined by molecular replacement method and shows the overall folding with four □-sheets surrounded by six □-helices. The model contains 149 residues of a total 152 residues and averaged 18 water molecules. Hexameric molecular packing in both crystals and solution implies the rice NDKs function as hexamers. In this study, we have determined the first rice NDK structure, which provides the detailed structural-functional information to understand the functional significance of this enzyme during plants growth and development in rice as well as plants.