Phosphorylation of ribosomal protein S6 at multiple sites by a cyclic AMP-independent protein kinase from lymphoid cells.
Phosphorylation of ribosomal protein S6 at multiple sites by a cyclic AMP-independent protein kinase from lymphoid cells.
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来自淋巴样细胞的不依赖于环 AMP 的蛋白激酶使核糖体蛋白 S6 在多个位点发生磷酸化。
DOI：
10.1016/s0021-9258(17)43679-9
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
R. Masaracchia
中科院分区：
文献类型：
--
作者：
M. Donahue;R. Masaracchia
从小鼠淋巴肉瘤细胞制备的核糖体被磷酸化的环AMP-独立的蛋白激酶命名为H4 P激酶。H4 P激酶是一种被Mg ~（2+）-ATP和内源性转化酶激活的失活酶。在没有Mg 2 +-ATP和内源性转化酶的预活化下，H4 P激酶以低速率催化80、60和40 S核糖体亚基的磷酸化。活化后，H4 P激酶选择性地催化40 S核糖体亚基中S6蛋白的磷酸化。在选定的测定条件下，转移至40 S核糖体制备物的[32 P]磷酸至少有90%掺入S 6。H4 P激酶磷酸化的40个S亚基的表观Km为7.2 μ M。计算的Vmax为50 nmol Pi转移/min/mg。40个S亚基的彻底磷酸化导致每摩尔S 6掺入3摩尔磷酸盐，与先前报道的结果相反，先前报道的结果表明0.3摩尔磷酸盐被来自网织红细胞的类似酶转移（Del Grande，R. W.，和Traugh，J. A.（1982）Eur. 123，421-428）。这些数据与H4 P激酶在胰岛素介导的S6多位点磷酸化中的潜在作用一致。
Ribosomes prepared from murine lymphosarcoma cells were phosphorylated by a cyclic AMP-independent protein kinase designated H4P kinase. H4P kinase was isolated as an inactive enzyme which was activated by Mg2+-ATP and an endogenous converting enzyme. In the absence of preactivation by Mg2+-ATP and an endogenous converting enzyme, H4P kinase catalyzed phosphorylation of 80, 60, and 40 S ribosomal subunits at a low rate. After activation, the H4P kinase selectively catalyzed phosphorylation of the S 6 protein in the 40 S ribosomal subunit. Under the assay conditions selected, at least 90% of the [32P]phosphate transferred to the 40 S ribosomal preparation was incorporated into S 6. The apparent Km for 40 S subunits phosphorylated by H4P kinase was 7.2 microM. The calculated Vmax was 50 nmol of Pi transferred per min/mg. Exhaustive phosphorylation of 40 S subunits resulted in incorporation of 3 mol of phosphate/mol of S 6, in contrast to results reported previously which indicated 0.3 mol of phosphate was transferred by a similar enzyme from reticulocyte (Del Grande, R. W., and Traugh, J. A. (1982) Eur. J. Biochem. 123, 421-428). These data are consistent with a potential role for H4P kinase in the insulin-mediated phosphorylation of S 6 at multiple sites.