Ratka M, Lackmann M, Ueckermann C, Karlins U, Koch G
Department of Molecular Biology, University of Hamburg, Federal Republic of Germany.
J Virol. 1989 Sep;63(9):3954-60. doi: 10.1128/JVI.63.9.3954-3960.1989.
The previously described poliovirus-associated protein kinase activity phosphorylates viral proteins VP0 and VP2 as well as exogenous proteins in the presence of Mg2+. In this paper, the effect of Zn2+ on the phosphorylation reaction and the stability of the poliovirus capsid has been studied in detail and compared to that of Mg2+. Phosphorylation patterns of viral and other proteins depend on the divalent cation present. In the presence of Zn2+, phosphorylation of capsid proteins VP2 and VP4 is significantly higher while phosphorylation of VP0 and exogenous phosphate acceptor proteins is not detected. Our results indicate the activation of more than one virus-associated protein kinase by Zn2+. The ion-dependent behavior of the enzyme activities is observed independently of whether the virus was obtained from HeLa or green monkey kidney cells. The poliovirus capsid is destabilized by Zn2+. The destabilization leads to a substantially increased permeability of virus particles to ethidium bromide and RNase, concomitant with decreased infectivity of the sample. This alteration of the poliovirus capsid structure is a prerequisite for effective phosphorylation of viral capsid proteins. The increased level of phosphorylation of viral capsid proteins results in further destabilization of the viral capsid. As a result of the conformational changes, poliovirus-associated protein kinase activities dissociate from the virus particle. High-performance liquid chromatography-purified viral protein VP2 is phosphorylated by the released enzymes on serine, threonine, and tyrosine in the presence of Zn2+. We suggest that the destabilizing effect of phosphorylation on the viral capsid plays a role in uncoating of poliovirus.
先前描述的脊髓灰质炎病毒相关蛋白激酶活性在Mg2+存在的情况下可使病毒蛋白VP0和VP2以及外源蛋白发生磷酸化。在本文中，详细研究了Zn2+对磷酸化反应和脊髓灰质炎病毒衣壳稳定性的影响，并与Mg2+的影响进行了比较。病毒蛋白和其他蛋白的磷酸化模式取决于存在的二价阳离子。在Zn2+存在的情况下，衣壳蛋白VP2和VP4的磷酸化显著更高，而未检测到VP0和外源磷酸受体蛋白的磷酸化。我们的结果表明Zn2+激活了不止一种病毒相关蛋白激酶。无论病毒是从HeLa细胞还是绿猴肾细胞获得的，都观察到了酶活性的离子依赖性行为。Zn2+会使脊髓灰质炎病毒衣壳不稳定。这种不稳定导致病毒颗粒对溴化乙锭和核糖核酸酶的通透性大幅增加，同时样品的感染性降低。脊髓灰质炎病毒衣壳结构的这种改变是病毒衣壳蛋白有效磷酸化的前提条件。病毒衣壳蛋白磷酸化水平的增加导致病毒衣壳进一步不稳定。由于构象变化，脊髓灰质炎病毒相关蛋白激酶活性从病毒颗粒上解离。在Zn2+存在的情况下，经高效液相色谱纯化的病毒蛋白VP2会被释放的酶在丝氨酸、苏氨酸和酪氨酸上磷酸化。我们认为磷酸化对病毒衣壳的去稳定作用在脊髓灰质炎病毒的脱壳过程中起作用。
