CRYSTAL-STRUCTURE OF THE MS2 COAT PROTEIN DIMER - IMPLICATIONS FOR RNA-BINDING AND VIRUS ASSEMBLY
CRYSTAL-STRUCTURE OF THE MS2 COAT PROTEIN DIMER - IMPLICATIONS FOR RNA-BINDING AND VIRUS ASSEMBLY
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DOI：
10.1016/s0969-2126(01)00156-3
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发表时间：
1995-03-15
期刊：
影响因子：
5.7
通讯作者：
ELY, KR
中科院分区：
文献类型：
--
作者：
NI, CZ;SYED, R;ELY, KR
背景：RNA噬菌体中的外壳蛋白结合并包裹病毒RNA，并通过与RNA基因组中的RNA发夹结合，作为病毒复制酶的翻译抑制因子。由于其双重功能，MS2外壳蛋白是蛋白质- rna相互作用和蛋白质-蛋白质相互作用结构研究的有趣候选者。在本研究中，选择未组装的MS2外壳蛋白二聚体来分析抑制物活性和病毒组装。结果：在2.0埃的分辨率下确定了一种突变体MS2外壳蛋白的晶体结构，该蛋白在病毒组装中存在缺陷，但仍保持抑制活性。未组装的二聚体通过α -螺旋的交错和在单体之间的界面上形成的10股反平行β -片来稳定。在残基82上精氨酸取代色氨酸，形成了两个新的亚基间氢键，进一步稳定了二聚体。分子遗传学鉴定的识别残基位于β -片的整个位置。其中两个残基（Tyr85和Asn87）在未配体中移位，与Trp- >Arg突变位于相同的β -链上。结论：与组装病毒外壳蛋白的结构相比，残基85和87的取向差异提示在病毒组装的第一步对结合RNA进行了构象调整。残基82上的取代可能通过对衣壳中形成关键亚基间接触的环施加构象限制而影响病毒组装。
Background: The coat protein in RNA bacteriophages binds and encapsidates viral RNA, and also acts as translational repressor of viral replicase by binding to an RNA hairpin in the RNA genome. Because of its dual function, the MS2 coat protein is an interesting candidate for structural studies of protein-RNA interactions and protein-protein interactions, In this study, unassembled MS2 coat protein dimers were selected to analyze repressor activity and virus assembly.Results: The crystal structure of a mutant MS2 coat protein that is defective in viral assembly yet retains repressor activity has been determined at 2.0 Angstrom resolution. The unassembled dimer is stabilized by interdigitation of alpha-helices, and the formation of a 10-stranded antiparallel beta-sheet across the interface between monomers. The substitution of arginine for tryptophan at residue 82 results in the formation of two new inter-subunit hydrogen bonds that further stabilize the dimer. Residues that recognition, identified by molecular genetics, were located across the beta-sheet. Two of these residues (Tyr85 and Asn87) are displaced in the unliganded dimer and are located in the same beta-strand as the Trp-->Arg mutation.Conclusions: When compared with the structure of the coat protein in the assembled virus, differences in orientation of residues 85 and 87 suggest conformational adjustment on binding RNA in the first step of viral assembly. The substitution at residue 82 may affect virus assembly by imposing conformational restriction on the loop that makes critical inter-subunit contacts in the capsid.