Pérez-Estévez A, Díaz-Jullien C, Covelo G, Salgueiro M T, Freire M
Departamento de Bioquímica y Biología Molecular, Facultad de Biología, Universidad de Santiago, Santiago de Compostela, Spain.
J Biol Chem. 1997 Apr 18;272(16):10506-13. doi: 10.1074/jbc.272.16.10506.
Prothymosin alpha (ProTalpha) is an acidic protein involved in cell proliferation. Its phosphorylation status is correlated with proliferative activity. Here we report the isolation and characterization of a ProTalpha-phosphorylating kinase (ProTalphaK) from mouse splenocytes that seems to be responsible for the in vivo phosphorylation of ProTalpha and that differs from other protein kinases reported to date. This enzyme, mainly located in the cytosol, has an molecular mass of 180 kDa and appears to be made up of two proteins of 64 and 60 kDa. Its activity was markedly enhanced by mitogenic activation of cells. The ProTalpha residues phosphorylated by the enzyme in vitro are a Thr at position 7 and another Thr at positions 12 or 13, both located within casein kinase 2 (CK-2) consensus motifs; these are the same residues as are phosphorylated in vivo. The new enzyme shows a number of clear structural and catalytic differences from CK-2. It phosphorylates histones H2B and H3, although with weaker activity than ProTalpha. An enzyme with the same characteristics was also found in other murine tissues and cell lines.
前胸腺素α（ProTα）是一种参与细胞增殖的酸性蛋白。其磷酸化状态与增殖活性相关。在此，我们报告从小鼠脾细胞中分离并鉴定出一种ProTα磷酸化激酶（ProTαK），它似乎负责ProTα在体内的磷酸化，且与迄今报道的其他蛋白激酶不同。这种酶主要位于胞质溶胶中，分子量为180 kDa，似乎由64 kDa和60 kDa的两种蛋白质组成。细胞的促有丝分裂激活可显著增强其活性。该酶在体外磷酸化的ProTα残基是第7位的苏氨酸以及第12或13位的另一个苏氨酸，这两个残基均位于酪蛋白激酶2（CK - 2）共有基序内；这些与体内磷酸化的残基相同。这种新酶与CK - 2在结构和催化方面存在许多明显差异。它能磷酸化组蛋白H2B和H3，尽管活性比ProTα弱。在其他小鼠组织和细胞系中也发现了具有相同特征的酶。
