The crystal structure of a human nucleoside diphosphate kinase, NM23-H2.
The crystal structure of a human nucleoside diphosphate kinase, NM23-H2.
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DOI：
10.1006/jmbi.1995.0457
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发表时间：
1995-08
影响因子：
5.6
通讯作者：
Philip A. Webb;O. Perisic;Chairmaine E. Mendola;J. Backer;Roger L. Williams
中科院分区：
文献类型：
--
作者：
Philip A. Webb;O. Perisic;Chairmaine E. Mendola;J. Backer;Roger L. Williams
利用粘球菌（Myxococcus xanthus）核苷二磷酸（NDP）激酶的结构，通过分子置换法测定了NM 23-H2的2.8 A分辨X射线结构。NM 23-H2是人NDP激酶。该酶催化磷酰基转移，结合DNA，并可在体外激活c-myc癌基因的转录。据报道，NM 23在某些类型的肿瘤中是转移的抑制因子。而M. Xanthus NDP激酶是四聚体，NM 23-H2是六聚体。NM 23-H2的折叠与其他NDP激酶的折叠相同。两个反向平行的螺旋通过一个转角连接形成核苷酸结合裂缝的一个边缘。该区域响应于衬底结合和晶体堆积力以铰链状方式移动。NDP激酶之间构象的其他差异主要在寡聚体内涉及蛋白质-蛋白质接触的区域中。在所有NDP激酶中唯一保守的蛋白质-蛋白质相互作用是二聚体相互作用。已经在肿瘤组织中检测到几种NM 23-H2突变。这些突变不涉及与底物相互作用的残基，并且可能使酶不稳定而不直接影响催化活性。已经报道了NM 23在体外和体内的低水平丝氨酸磷酸化。六聚体的结构表明，两个丝氨酸残基，已被报道为磷酸化，Ser 44和Ser 122，是在六聚体的表面上，并可能被外源激酶磷酸化。相比之下，Ser 120被掩埋，并且最有可能通过从反应机制的磷酸组氨酸中间体直接转移而磷酸化。
The 2.8 A resolution X-ray structure of NM23-H2 has been determined by molecular replacement using the structure of Myxococcus xanthus nucleoside diphosphate (NDP) kinase. NM23-H2 is a human NDP kinase. The enzyme catalyses phosphoryl transfer, binds DNA, and can activate the transcription of the c-myc oncogene in vitro. NM23 has also been reported to be a suppressor of metastasis in some types of tumours. Whereas the M. xanthus NDP kinase is a tetramer, NM23-H2 is a hexamer. The fold of NM23-H2 is identical to the fold of other NDP kinases. Two antiparallel helices joined by a turn form one edge of the nucleotide binding cleft. This region moves in a hinge-like fashion in response to substrate binding and crystal packing forces. Additional differences in conformation among the NDP kinases are principally in regions involved in protein-protein contacts within the oligomers. The only protein-protein interaction conserved among all NDP kinases is a dimeric interaction. Several mutations of NM23-H2 have been detected in tumour tissues. These mutations do not involve residues interacting with the substrates, and probably destabilise the enzyme without directly affecting the catalytic activity. Low level phosphorylation of serines has been reported for NM23 both in vitro and in vivo. The structure of the hexamer indicates that two serine residues that have been reported as being phosphorylated, Ser44 and Ser122, are on the surface of the hexamer, and are likely to be phosphorylated by exogenous kinases. In contrast, Ser120 is buried, and is most likely phosphorylated by a direct transfer from the phosphohistidine intermediate of the reaction mechanism.