Beckett D, Wu H N, Uhlenbeck O C
University of Colorado, Department of Chemistry and Biochemistry, Boulder 80309-0215.
J Mol Biol. 1988 Dec 20;204(4):939-47. doi: 10.1016/0022-2836(88)90053-8.
In order to understand the role of sequences other than the translational operator on bacteriophage R17 assembly, in vitro capsid assembly was studied with R17 coat protein and a variety of RNAs. For a series of RNA oligomers of the same chain length, sequences that bind coat protein dimer with a lower affinity require higher concentrations of RNA and protein for assembly. Among a series of non-specific RNA molecules of differing lengths, lower protein and RNA concentrations are required for assembly of capsids containing longer RNAs. For RNA molecules of any length, the presence of a single high-affinity translational operator sequence lowered the concentration requirements for capsid assembly. However, the advantage for encapsidation provided by the operator sequence is small for large RNA molecules. The experiments indicate that in the overall assembly process the interaction of coat protein with non-specific sequences is at least as important as its interaction with the specific translational operator sequence. In light of the data, a mechanism of achieving selective packaging of the R17 genomic RNA in vivo is discussed.
为了了解除翻译操纵子之外的序列在噬菌体R17组装中的作用，利用R17衣壳蛋白和多种RNA对体外衣壳组装进行了研究。对于一系列链长相同的RNA寡聚物，与衣壳蛋白二聚体结合亲和力较低的序列在组装时需要更高浓度的RNA和蛋白质。在一系列不同长度的非特异性RNA分子中，组装含有较长RNA的衣壳所需的蛋白质和RNA浓度较低。对于任何长度的RNA分子，单个高亲和力翻译操纵子序列的存在降低了衣壳组装的浓度要求。然而，对于大RNA分子，操纵子序列提供的衣壳化优势较小。实验表明，在整个组装过程中，衣壳蛋白与非特异性序列的相互作用至少与其与特异性翻译操纵子序列的相互作用同样重要。根据这些数据，讨论了在体内实现R17基因组RNA选择性包装的机制。
