杆状病毒蛋白激酶的特性和核心蛋白的磷酸化及去磷酸化

CHARACTERIZATION OF A BACULOVIRUS PROTEIN KINASE AND PHOSPHORYLATION AND DE-PHOSPHORYLATION OF THE VIRUS BASIC CORE PROTEIN

粉纹夜蛾核型多角体病毒(Trichoplusia ni Nuclear Polyhedrosis Virus,TnNPV)的两种病毒粒子,即细胞释放毒粒(Cell released virus,CRV)与除去多角体蛋白的毒粒(多角体衍生毒拉Polyhedron-derived virus,PDV)均带有蛋白激酶。这种激酶不赖于环核苷酸,能在不同的pH值和Mg^(++)离子浓度下以ATP为供体,磷酸化蛋白肽链中的丝氨酸和苏氨酸。应用毒粒的与受感染草地贪夜蛾(Spodoptera frugiperda)细胞中的蛋白激酶,对自身蛋白多肽磷酸化的结果表明,病毒核心碱性蛋白是主要的磷酸体受体之一。用[^(32)P]磷酸盐标记活体细胞,亦能检出细胞内磷酸化的病毒核心蛋白,但从标记的细胞中分离CRV,发现这些毒粒的核心蛋白并不是磷酸化的,说明TnNPV在细胞内复制过程中,磷酸基团转至核心蛋白后,毒粒组装前又去磷酸化。本文还对上述动态磷酸化过程及其在病毒复制中的作用进行了讨论。

Cell-released and polyhedron-derived forms of Trichoplusia ni Nuclear Polyhedrosis Virus ( TnNPV)particles possess protein kinase activity and the activity was not enhanced by cyclic nucleotide. The Mg++ cation and pH optima for the protein kinase activity,which catalyzes the pho sphate bound to serine and threonine, was determined and found to be not particularly stringent. Phosphorylation of the virus basie core protein were also found in this study, regardless of whether the kinases used were from virus particles or infected cell extracts and whether phosphorylation was carried out in vitro or in vivo.The demonstration that phosphory1ation of the basie protein occured in most cases but not detected in purified [32p] orthophosphate-labelled virus suggests that de-phosphorylation of the protein takes place before virus packaging. The role for de-phosphorylation of the basie protein is discussed.