Novak Christopher R, Fane Bentley A
Department of Veterinary Science and Microbiology, University of Arizona, Building 90, Tucson, AZ 85721, USA.
J Mol Biol. 2004 Jan 2;335(1):383-90. doi: 10.1016/j.jmb.2003.09.050.
phiX174 utilizes two scaffolding proteins during morphogenesis, an internal protein (B) and an external protein (D). The B protein induces a conformational change in coat protein pentamers, enabling them to interact with both spike and external scaffolding proteins. While functions of the carboxyl terminus of protein B have been defined, the functions of the amino terminus remain obscure. To investigate the morphogenetic functions of the amino terminus, several 5' deleted genes were constructed and the proteins expressed in vivo. The DeltaNH(2) B proteins were assayed for the ability to complement an ochre B mutant and defects in the morphogenetic pathway were characterized. The results of the biochemical, genetic and second-site genetic analyses indicate that the amino terminus induces conformational changes in the viral coat protein and facilitates minor spike protein incorporation. Defects in conformational switching can be suppressed by substitutions in the external scaffolding protein, suggesting some redundancy of function between the two proteins.
φX174在形态发生过程中利用两种支架蛋白，一种是内部蛋白（B），另一种是外部蛋白（D）。B蛋白诱导衣壳蛋白五聚体发生构象变化，使其能够与刺突蛋白和外部支架蛋白相互作用。虽然蛋白B羧基末端的功能已经明确，但氨基末端的功能仍不清楚。为了研究氨基末端的形态发生功能，构建了几个5'端缺失的基因，并在体内表达这些蛋白。对缺失氨基末端的B蛋白（DeltaNH(2) B）进行了互补赭石型B突变体能力的检测，并对形态发生途径中的缺陷进行了表征。生化、遗传和第二位点遗传分析结果表明，氨基末端诱导病毒衣壳蛋白发生构象变化，并促进小刺突蛋白的掺入。外部支架蛋白中的替代可以抑制构象转换缺陷，这表明这两种蛋白之间存在一些功能冗余。
