Subunit interactions in southern bean mosaic virus.
Subunit interactions in southern bean mosaic virus.
复制标题
南方豆花叶病毒的亚基相互作用。
DOI：
10.1016/s0022-2836(83)80049-7
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发表时间：
1983
影响因子：
5.6
通讯作者：
Erickson,JW
中科院分区：
文献类型：
--
作者：
Rossmann,MG;Abad-Zapatero,C;Hermodson,MA;Erickson,JW
南方菜豆花叶病毒（Southern bean mosaic virus）的三个准等价亚基A、B和C的结构是根据电子密度图精心构建的，该电子密度图已经用三个循环的分子置换平均法进行了细化。用氨基酸序列和计算机图形系统对图谱进行了解释，发现除了羧基末端残基“铰链”中的5个残基外，三个准等价亚基的构象几乎相同。将衣壳中亚基之间的接触制表并分析。最大数量的相互作用是在5倍相关亚基之间。尽管准3倍或准6倍相关亚基具有几乎相同的接触数。2倍轴上的相互作用要少得多。亚基间存在着大量的电荷相互作用和大量的氢键，A亚基间的二十面体5重相互作用（AA 5）和C亚基与B亚基间的准6重相互作用（CB 5）基本相同。含有C亚基（B2C）的插入有序βA臂的准6重相互作用是完全不同的。有一个“旋转矢量”或接触线，C和B亚基围绕它旋转以形成CB 5或B2C相互作用。类似的情况涉及准2重接触AB 5和二十面体2重接触CC 2之间的关系。在两种情况下，绕铰链的旋转量为36°至39°。准3重接触BA和AC基本上相同，但与BC接触略有不同，但差异显著。后者亚基间有额外的5°旋转，推测亚基二聚体的“松弛”AB_5构象可能自组装成由5个二聚体围绕5倍轴组成的10聚体帽，RNA与基本的随机结构域和壳结构域的基本内表面结合。这10聚体可能成核组装的T =1或T =3衣壳，这取决于在亚基接触区的羧基簇的电荷状态。在低电荷状态下，形成T=1衣壳。或者，在高电荷状态下，二聚体必须“张紧”，如天然病毒的CC 2接触，以结合10聚体帽，产生疏水通道以诱导βA臂的有序化和β环的形成。病毒外壳蛋白中二聚体的双态条件扩展了Caspar & Klug（1962）最初设想的结构范围。附录I考虑了病毒RNA与外壳蛋白相互作用的可能方式。南方菜豆花叶病毒外壳蛋白表面上的一种面对RNA的碱性残基模式能够以令人惊讶的准确性对接一个九个碱基对的双螺旋A-RNA结构。每个碱性残基与不同的磷酸盐相关，蛋白质可以与小沟中的五个碱基相互作用。有人提出，这是RNA与南方菜豆花叶病毒外壳蛋白相互作用的少数方式之一。
The structures of the three quasi-equivalent subunits A, B and C of southern bean mosaic virus have been carefully built in accordance with an electron density map that had been refined with three cycles of molecular replacement averaging. The map was interpreted with the aid of the amino acid sequence and a computer graphics system.The three quasi-equivalent subunits were compared in pairs and found to have almost the same conformation except for five residues in the carboxy-terminal vestigial “hinge”. Contacts between subunits in the capsid were tabulated and analyzed. The largest number of interactions was between the 5-fold-related subunits. although the quasi-3-fold or quasi-6-fold-related subunits had nearly the same number of contacts. The interactions across the 2-fold axes were far fewer. A number of charge interactions and numerous hydrogen-bonding possibilities exist in the subunit interactions.The icosahedral 5-fold interactions between A subunits (AA5) and the quasi-6-fold interactions between C and B subunits without the interposed βA arm (CB5) are essentially identical. The quasi-6-fold interactions containing the interposed ordered βA arm of the C subunit (B2C) are quite different. There is a “vector of rotation” or line of contact about which the C and B subunits rotate to form either CB5or B2C interactions. A similar situation pertains to the relationship between the quasi-2-fold contacts AB5and the icosahedral 2-fold contacts CC2. The amount of rotation about the hinge is 36° to 39° in both cases. The quasi-3-fold contacts BA and AC are essentially identical but differ slightly but significantly from the BC contacts. The latter have an additional 5° rotation between subunits.It is proposed that the “relaxed” AB5conformation of subunit dimers might self-assemble into 10mer caps composed of five dimers about a 5-fold axis with RNA binding to the basic random domain and the basic interior surface of the shell domain. This 10mer might nucleate the assembly of aT=1 orT=3 capsid, depending on the charge state of carboxyl group clusters in the subunit contact region. In the low charge state,T=1 capsids are formed. Alternatively, in the high charge state, dimers must be “tensed”, as in the CC2contacts of the native virus, for binding to the 10mer cap, creating a hydrophobic channel to induce the ordering of the βA arm and formation of the β-annulus. The two-state condition of dimers in a viral coat protein extends the range of structures originally envisaged by Caspar & Klug (1962).Appendix I considers a possible manner in which viral RNA might interact with the coat protein. A pattern of basic residues on the southern bean mosaic virus coat protein surface facing the RNA is able to dock a nine base-pair double-helicalA-RNA structure with surprising accuracy. The basic residues are each associated with a different phosphate and the protein can make interactions with five bases in the minor groove. It is proposed that this is one of a small number of ways in which the RNA interacts with southern bean mosaic virus coat protein.
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影响因子：
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