Valegård K, Murray J B, Stockley P G, Stonehouse N J, Liljas L
Department of Molecular Biology, Uppsala University, Sweden.
Nature. 1994 Oct 13;371(6498):623-6. doi: 10.1038/371623a0.
The RNA bacteriophage MS2 is a convenient model system for the study of protein-RNA interactions. The MS2 coat protein achieves control of two distinct processes--sequence-specific RNA encapsidation and repression of replicase translation--by binding to an RNA stem-loop structure of 19 nucleotides containing the initiation codon of the replicase gene. The binding of a coat protein dimer to this hairpin shuts off synthesis of the viral replicase, switching the viral replication cycle to virion assembly rather than continued replication. The operator fragment alone can trigger self-assembly of the phage capsid at low protein concentrations and a complex of about 90 RNA operator fragments per protein capsid has been described. We report here the crystal structure at 3.0 A resolution of a complex between recombinant MS2 capsids and the 19-nucleotide RNA fragment. It is the first example of a structure at this resolution for a sequence-specific protein-RNA complex apart from the transfer RNA synthetase complexes. The structure shows sequence-specific interactions between conserved residues on the protein and RNA bases essential for binding.
RNA噬菌体MS2是研究蛋白质-RNA相互作用的便捷模型系统。MS2外壳蛋白通过与包含复制酶基因起始密码子的19个核苷酸的RNA茎环结构结合，实现对两个不同过程的控制——序列特异性RNA包装和复制酶翻译的抑制。外壳蛋白二聚体与该发夹的结合会关闭病毒复制酶的合成，将病毒复制周期切换到病毒粒子组装而非持续复制。单独的操纵子片段在低蛋白浓度下就能触发噬菌体衣壳的自组装，并且已经描述了每个蛋白质衣壳约有90个RNA操纵子片段的复合物。我们在此报告重组MS2衣壳与19核苷酸RNA片段复合物在3.0埃分辨率下的晶体结构。这是除了转移RNA合成酶复合物之外，该分辨率下序列特异性蛋白质-RNA复合物结构的首个实例。该结构显示了蛋白质上保守残基与结合所必需的RNA碱基之间的序列特异性相互作用。
