Effects of polyamines on prostatic chromatin- and non-histone-protein-associated protein kinase reactions.
Effects of polyamines on prostatic chromatin- and non-histone-protein-associated protein kinase reactions.
复制标题
多胺对前列腺染色质和非组蛋白相关蛋白激酶反应的影响。
作者：
K. Ahmed;M. Wilson;S. Goueli;H. G. Williams
研究多胺对前列腺染色质和非组蛋白相关蛋白激酶反应的影响，涉及外源性和内源性底物。在160- 200 mM-NaCl（或-KCl或-NH_4Cl）浓度下，对模型酸性蛋白底物脱磷酸卵黄蛋白酶活性最高。在这些条件下，亚精胺和精胺添加浓度高达2 mM基本上没有影响。然而，在不向培养基中加入NaCl的情况下，这些多胺在1- 2 mM浓度下引起这些反应的显著刺激。这种刺激效应不是由于离子强度的非特异性变化或精胺取代Mg ~（2+）所致，因为只有在最佳（2- 4 mM）Mg ~（2+）浓度下才观察到1 mM精胺的最大刺激。从去势大鼠前列腺的酶制剂，并与染色质和非组蛋白的蛋白质制剂，除了腹侧前列腺的其他组织中观察到类似的效果的多胺。当内源性非组蛋白的染色质的磷酸化进行测量，精胺刺激的初始速率和最终的转磷酸化程度，即使在最佳浓度的NaCl的存在下。相比之下，精胺或亚精胺对染色质和非组蛋白相关的蛋白激酶反应没有影响，以富含赖氨酸的组蛋白为底物。化学NN-二甲基化dephosphophosvitin是一个活性较低的底物染色质相关的蛋白激酶，但其磷酸化更显着刺激精胺相比，未修饰的dephosphophosvitin。这些观察结果表明，多胺刺激的各种蛋白激酶反应可能是由于对构象的非组蛋白底物，而不是对激酶本身的影响。
Studies are presented on the influence of polyamines on prostatic chromatin- and non-histone-protein-associated protein kinase reactions involving both exogenous and endogenous substrates. The activities toward the model acidic protein substrate, dephosphophosvitin, were maximal at 160--200mM-NaCl (or -KCl or -NH4Cl). Under these conditions, spermidine and spermine added in concentrations up to 2mM were essentially without effect. However, without addition of NaCl to the medium, marked stimulation of these reactions was elicited by these polyamines at 1--2mM concentrations. The stimulatory effects were not due to non-specific changes in the ionic strength or to substitution of spermine for Mg2+, as maximal stimulation by 1 mM-spermine was observed only at optimal (2--4mM) Mg2+ concentrations. Qualitatively similar effects of polyamines were observed with enzyme preparations from the prostates of castrated rats, and with chromatin and non-histone-protein preparations from other tissues besides ventral prostate. When phosphorylation of endogenous non-histone proteins of the chromatin was measured, spermine stimulated both the initial rates and the final extent of transphosphorylation, even in the presence of optimal concentration of NaCl. By contrast, spermine or spermidine had no effect on the chromatin- and non-histone-protein-associated protein kinase reactions determined with lysine-rich histones as substrates. Chemically NN-dimethylated dephosphophosvitin was a less active substrate for the chromatin-associated protein kinase, but its phosphorylation was more markedly stimulated by spermine in comparison with unmodified dephosphophosvitin. These observations hint that the polyamine stimulations of the various protein kinase reactions may be due to effects on the conformations of the non-histone protein substrates rather than on the kinases themselves.