A NOVEL SERINE THREONINE-SPECIFIC PROTEIN PHOSPHOTRANSFERASE ACTIVITY OF NM23 NUCLEOSIDE-DIPHOSPHATE KINASE
A NOVEL SERINE THREONINE-SPECIFIC PROTEIN PHOSPHOTRANSFERASE ACTIVITY OF NM23 NUCLEOSIDE-DIPHOSPHATE KINASE
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DOI：
10.1111/j.1432-1033.1995.200_c.x
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发表时间：
1995-11-15
期刊：
影响因子：
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通讯作者：
WELTER, C
中科院分区：
文献类型：
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作者：
ENGEL, M;VERON, M;WELTER, C
已经鉴定了两个人nm 23基因，命名为nm 23-H1和nm 23-H2，它们分别编码88%相同的核苷二磷酸激酶（NDPK）A和NDPK B多肽。nm 23-H1基因产物已被证明在抑制肿瘤转移中发挥功能性作用。Nm 23蛋白/NDPK在整个进化过程中高度保守，并参与控制各种物种的细胞分化和发育，但其潜在机制尚未确定。无论是NDPK活性还是最近发现的NDPK B的DNA结合活性，都不能令人满意地解释Nm 23的调节功能。本研究提供的证据表明，纯化的Nm 23蛋白能够转移磷酸基团的其他蛋白质时，非变性量的尿素存在。这种新的Nm 23/NDPK活性被发现是特定的丝氨酸和苏氨酸残基，和底物蛋白的转磷酸化发生化学计量。由于不存在底物转换，新功能被称为蛋白磷酸转移酶活性而不是蛋白激酶活性。这表明尿素刺激NDPK与其他蛋白质的相互作用。使用纯化的NDPK制剂从人，果蝇，酵母和Dictyosteoprotein在尿素的存在下，获得相同的磷蛋白模式。从人红细胞中部分纯化的NDPK产生了类似的磷酸化模式，不依赖于尿素的加入，也起化学计量作用。在该制剂中，Nm 23种类的蛋白磷酸转移酶活性可能通过与共纯化蛋白的相互作用而产生和/或稳定。使用不同的突变体的网囊藻NDPK，它表明，蛋白质磷酸转移酶活性取决于相同的活性位点的NDPK活性。提出了一种类似于蛋白质-组氨酸激酶的磷酸转移机制，涉及高能磷酸组氨酸中间体。此外，新的Nm 23功能进行了比较，与一个明显类似的蛋白磷酸转移酶的活性，这是以前观察到的部分纯化的NDPK从不同的植物物种。
Two human nm23 genes have been identified, designated nm23-H1 and nm23-H2, which encode the 88% identical nucleoside-diphosphate kinase (NDPK) A and NDPK B polypeptides, respectively. The nm23-H1 gene product has been shown to play a functional role in the suppression of tumor metastasis. The Nm23 proteins/NDPK are highly conserved throughout evolution and are implicated in controling cellular differentiation and development in various species, while the underlying mechanisms remain undefined. Neither the NDPK activity nor the DNA-binding activity, identified recently for NDPK B, can satisfactory explain the regulatory functions of Nm23. The present study provides evidence that purified Nm23 proteins are capable of transferring a phosphate group to other proteins when non-denaturing amounts of urea are present. This novel Nm23/NDPK activity was found to be specific for serine and threonine residues, and the transphosphorylation of substrate proteins occurred stoichiometrically. Because of the absence of a substrate turn-over, the novel function was termed protein phosphotransferase activity instead of protein kinase activity. It is demonstrated that urea stimulates the interaction of NDPK with other proteins. Identical phosphoprotein patterns were obtained using purified NDPK preparations from human, Drosophila, yeast and Dictyostelium in the presence of urea. Partially purified NDPK from human erythrocytes produced a similar phosphorylation pattern independent of urea addition and also acted stoichiometrically. In this preparation, a protein phosphotransferase activity of Nm23 species may possibly be generated and/or stabilized by the interaction with copurified proteins. Using different mutants of Dictyostelium NDPK it was shown that the protein phosphotransferase activity depends on the same active site as the NDPK activity. A phosphotransfer mechanism analogous to that Of protein-histidine kinases is proposed, involving a high-energy phosphohistidine intermediate. Furthermore, the novel Nm23 function is compared with an apparently similar protein phosphotransferase activity which was observed previously with partially purified NDPK from different plant species.