Structural studies of bacteriophage α3 assembly
Structural studies of bacteriophage α3 assembly
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DOI：
10.1016/s0022-2836(02)01201-9
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发表时间：
2003-01-03
影响因子：
5.6
通讯作者：
Rossmann, MG
中科院分区：
文献类型：
--
作者：
Bernal, RA;Hafenstein, S;Rossmann, MG
噬菌体α3是小病毒科的成员，小病毒科是包括phiX174在内的一个小的单链二十面体噬菌体家族。这些病毒有一个与大约12个拷贝的H引导蛋白和60个拷贝的小J DNA结合蛋白相关的单链DNA基因组。衣壳周围有60个F外壳蛋白，上面装饰着12个五聚体的G蛋白。组装通过108个S空的前壳蛋白进行，需要外部的D和内部的B支架蛋白来形成。用冷冻电子显微镜(Cryo-EM)检测到分辨率为15埃的α3“开放”前壳蛋白结构中间体。与phiX174“封闭”的proapsid和感染性病毒粒子不同，alpha3开放proapsid的3倍顶端有30埃宽的毛孔，由于F衣壳蛋白中两个螺旋的无序，F五聚体之间有20埃宽的间隙。在DNA包装过程中，大孔可能用于DNA进入和内部支架蛋白退出。B支架蛋白的一部分位于棘突下方的5倍轴线上，位于衣壳内表面的疏水口袋中。蛋白B似乎具有自身蛋白分解活性，该活性在Arg-Phe基序处裂解，可能有助于蛋白质通过30埃宽的孔被移除。用X射线结晶学将α3成熟病毒粒子的结构解析到3.5埃分辨率，并用其解释开放的proapsid冷冻-EM结构。α3和phiX174病毒粒子结构之间的主要区别在于尖峰蛋白和DNA结合蛋白。与phiX174相比，字母3五聚体尖峰的旋转角度为3.5度。与phiX174 J蛋白相比，alpha3 DNA结合蛋白的氨基末端短13个氨基酸残基，在衣壳蛋白的内表面保留了其羧基末端结合部位。与phiX174相比，单链DNA的二十面体有序结构成分在α3中似乎显著增加，允许构建约10%的核糖-磷酸骨架。(C)2002爱思唯尔科学有限公司。保留所有权利。
Bacteriophage alpha3 is a member of the Microviridae, a family of small, single-stranded, icosahedral phages that include phiX174. These viruses have an ssDNA genome associated with approximately 12 copies of an H pilot protein and 60 copies of a small J DNA-binding protein. The surrounding capsid consists of 60 F coat proteins decorated with 12 pentameric spikes of G protein. Assembly proceeds via a 108 S empty procapsid that requires the external D and internal B scaffolding proteins for its formation.The alpha3 "open" procapsid structural intermediate was determined to 15 Angstrom resolution by cryo-electron microscopy (cryo-EM). Unlike the phiX174 "closed" procapsid and the infectious virion, the alpha3 open procapsid has 30 Angstrom wide pores at the 3-fold vertices and 20 Angstrom wide gaps between F pentamers as a result of the disordering of two helices in the F capsid protein. The large pores are probably used for DNA entry and internal scaffolding protein exit during DNA packaging. Portions of the B scaffolding protein are located at the 5-fold axes under the spike and in the hydrophobic pocket on the inner surface of the capsid. Protein B appears to have autoproteolytic activity that cleaves at an Arg-Phe motif and probably facilitates the removal of the protein through the 30 Angstrom wide pores.The structure of the alpha3 mature virion was solved to 3.5 Angstrom resolution by X-ray crystallography and was used to interpret the open procapsid cryo-EM structure. The main differences between the alpha3 and phiX174 virion structures are in the spike and the DNA-binding proteins. The alpha3 pentameric spikes have a rotation of 3.5degrees compared to those of phiX174. The alpha3 DNA-binding protein, which is shorter by 13 amino acid residues at its amino end when compared to the phiX174 J protein, retains its carboxyterminal-binding site on the internal surface of the capsid protein. The icosahedrally ordered structural component of the ssDNA appears to be substantially increased in alpha3 compared to phiX174, allowing the building of about 10% of the ribose-phosphate backbone. (C) 2002 Elsevier Science Ltd. All rights reserved.