Robinson Mark A, Wood Jonathan P A, Capaldi Stephanie A, Baron Andrew J, Gell Christopher, Smith D Alastair, Stonehouse Nicola J
Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
Nucleic Acids Res. 2006 May 19;34(9):2698-709. doi: 10.1093/nar/gkl318. Print 2006.
DNA packaging in the bacteriophage phi29 involves a molecular motor with protein and RNA components, including interactions between the viral connector protein and molecules of pRNA, both of which form multimeric complexes. Data are presented to demonstrate the higher order assembly of pRNA together with the affinity of pRNA:pRNA and pRNA:connector interactions, which are used to propose a model for motor function. In solution, pRNA can form dimeric and trimeric multimers in a magnesium-dependent manner, with dissociation constants for multimerization in the micromolar range. pRNA:connector binding is also facilitated by the presence of magnesium ions, with a nanomolar apparent dissociation constant for the interaction. From studies with a mutant pRNA, it appears that multimerization of pRNA is not essential for connector binding and it is likely that connector protein is involved in the stabilization of higher order RNA multimers. It is proposed that magnesium ions may promote conformational change that facilitate pRNA:connector interactions, essential for motor function.
噬菌体phi29中的DNA包装涉及一个由蛋白质和RNA成分组成的分子马达，包括病毒连接蛋白与pRNA分子之间的相互作用，二者均可形成多聚体复合物。本文提供的数据展示了pRNA的高阶组装以及pRNA:pRNA和pRNA:连接蛋白相互作用的亲和力，据此提出了一个分子马达功能模型。在溶液中，pRNA能够以镁离子依赖的方式形成二聚体和三聚体多聚体，多聚化的解离常数在微摩尔范围内。镁离子的存在也促进了pRNA与连接蛋白的结合，该相互作用的表观解离常数为纳摩尔级别。通过对突变型pRNA的研究发现，pRNA的多聚化对于连接蛋白的结合并非必不可少，连接蛋白可能参与了高阶RNA多聚体的稳定。有人提出，镁离子可能促进构象变化，从而有利于pRNA与连接蛋白的相互作用，这对分子马达功能至关重要。
