Butler P J, Lomonossoff G P
Biophys J. 1980 Oct;32(1):295-312. doi: 10.1016/S0006-3495(80)84958-7.
Assembly of tobacco mosaic virus is initiated by the binding of a specific loop of the RNA into the central hole of the disk aggregate of protein subunits. Since the nucleation loop is located about five-sixths along the RNA molecule, subsequent elongation must be bidirectional. We have now measured the rates of elongation in the two directions by determining the lengths of RNA protected from nuclease digestion at different times and using either intact TMV rNA, or RNA with most of the longer tail removed. Comparison of the rates with the protein supplied as either a mixture of disks with A-protein (a mixture of less aggregated states) or just A-protein, shows that different mechanisms and protein aggregates are used for the most rapid growth. When disks are present, they add more rapidly along the longer RNA tail but do not appear to add directly on the shorter tail. In contrast, smaller aggregates (A-protein) can add at both ends of the rod, but do so more slowly. Mechanisms for these processes are discussed. Preliminary results on the binding of the specific hexanucleotide AAGAAG to the disk are given and compared with the known changes on binding nonspecific hexanucleotides or the trinucleotide AAG.
烟草花叶病毒的组装是由RNA的特定环与蛋白质亚基盘状聚集体的中心孔结合引发的。由于成核环位于RNA分子约六分之五的位置，随后的延伸必定是双向的。我们现在通过测定在不同时间免受核酸酶消化的RNA长度，并使用完整的烟草花叶病毒RNA或去除了大部分较长尾部的RNA，来测量两个方向上的延伸速率。将这些速率与以含有A蛋白的盘状聚集体混合物（聚集程度较低的混合物）或仅A蛋白形式提供的蛋白质进行比较，结果表明，最快速生长时使用了不同的机制和蛋白质聚集体。当存在盘状聚集体时，它们沿着较长的RNA尾部添加得更快，但似乎不会直接添加到较短的尾部。相比之下，较小的聚集体（A蛋白）可以在杆的两端添加，但速度较慢。文中讨论了这些过程的机制。给出了特定六核苷酸AAGAAG与盘状聚集体结合的初步结果，并与已知的非特异性六核苷酸或三核苷酸AAG结合时的变化进行了比较。
