Galisteo M L, King J
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Biophys J. 1993 Jul;65(1):227-35. doi: 10.1016/S0006-3495(93)81073-7.
During the packaging of double-stranded DNA by bacterial viruses, the precursor procapsid loses its internal core of scaffolding protein and undergoes a substantial expansion to form the mature virion. Here we show that upon heating, purified P22 procapsids release their scaffolding protein subunits, and the coat protein lattice expands in the absence of any other cellular or viral components. Following these processes by differential scanning calorimetry revealed four different transitions that correlated with structural transitions in the coat protein shells. Exit of scaffolding protein from the procapsid occurred reversibly and just above physiological temperature. Expansion of the procapsid lattice, which was exothermic, occurred after the release of scaffolding protein. Partial denaturation of coat subunits within the intact shell structure was detected prior to the major endothermic event. This major endotherm occurred above 80 degrees C and represents particle breakage and irreversible coat protein denaturation. The results indicate that the coat subunits are designed to form a metastable precursor lattice, which appears to be separated from the mature lattice by a kinetic barrier.
在细菌病毒对双链DNA进行包装的过程中，前衣壳失去其内部的支架蛋白核心，并经历大幅膨胀以形成成熟的病毒粒子。在此我们表明，加热时，纯化的P22前衣壳会释放其支架蛋白亚基，并且衣壳蛋白晶格在没有任何其他细胞或病毒成分的情况下发生膨胀。通过差示扫描量热法追踪这些过程，发现了四个与衣壳蛋白壳层结构转变相关的不同转变。支架蛋白从前衣壳的释放是可逆的，且刚好发生在生理温度之上。衣壳晶格的膨胀是放热的，发生在支架蛋白释放之后。在主要吸热事件之前，检测到完整壳层结构内的衣壳亚基发生部分变性。这个主要吸热峰出现在80摄氏度以上，代表粒子破裂和衣壳蛋白的不可逆变性。结果表明，衣壳亚基被设计形成一个亚稳态的前体晶格，它似乎通过一个动力学屏障与成熟晶格相分离。
