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首页> 外文期刊>Biochemistry >DIMORPHISM OF HEPATITIS B VIRUS CAPSIDS IS STRONGLY INFLUENCED BY THE C-TERMINUS OF THE CAPSID PROTEIN
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DIMORPHISM OF HEPATITIS B VIRUS CAPSIDS IS STRONGLY INFLUENCED BY THE C-TERMINUS OF THE CAPSID PROTEIN

机译：甲壳素蛋白的C端强烈影响肝炎B病毒胶囊的异常

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Hepatitis B virus (HBV) is an enveloped virus with an icosahedral capsid. Its homodimeric capsid protein (''core antigen'') assembles into particles of two sizes, one with T = 3 icosahedral symmetry (90 dimers) and the other with T = 4 symmetry (120 dimers). We have investigated this assembly process in vitro, using a variety of purified, bacterially expressed, capsid proteins. All of our constructs lacked the predominantly basic C-terminal 34 amino acids of the full-length capsid protein (183 amino acids) and were further truncated to terminate at specific points between residues 138 and 149. While the smallest construct (138 residues) did not assemble into capsids, those terminating at residue 140, and beyond, assembled into mixtures of T = 3 and T = 4 particles. The two kinds of capsids could be separated on sucrose gradients and did not interconvert upon protracted storage. The proportion of T = 3 capsids, assayed by sucrose gradient fractionation, analytical ultracentrifugation and cryoelectron microscopy, was found to increase systematically with larger deletions from the C-terminus. The variant terminating at residue 149 formed similar to 5% of T = 3 capsids, while the 140-residue protein produced similar to 85% of this isomorph. For the 147-residue capsid protein, the structures of both capsids were determined to 17 Angstrom resolution by three-dimensional reconstruction of cryoelectron micrographs. In these density maps, the boundaries of the constituent dimers can be clearly seen and the quaternary structures of the two capsids compared. The arrangement of dimers around their icosahedral five-fold axes is almost identical, whereas the quasi-six-fold arrangements of dimers are distinctly different.
机译：乙型肝炎病毒（HBV）是带有二十面体衣壳的包膜病毒。其同二聚体衣壳蛋白（“核心抗原”）组装成两种大小的颗粒，一种具有T = 3二十面体对称性（90个二聚体），另一个具有T = 4对称性（120个二聚体）。我们已经使用多种纯化的，细菌表达的衣壳蛋白体外研究了该组装过程。我们所有的构建体都缺少全长衣壳蛋白的主要C末端34个氨基酸（183个氨基酸），并被进一步截短以终止于残基138和149之间的特定点。而最小的构建体（138个残基）确实存在不能组装成衣壳，那些在残基140和更高处终止的衣壳，组装成T = 3和T = 4颗粒的混合物。两种衣壳可以在蔗糖梯度上分离，并且在长期储存时不会相互转化。通过蔗糖梯度分级分离，分析超速离心和冷冻电子显微镜分析，发现T = 3衣壳的比例随着C末端的较大缺失而系统地增加。终止于残基149的变异体形成的T相似数目为5％，= 3个衣壳，而140残基的蛋白质产生的变异体接近此同构体的85％。对于147个残基的衣壳蛋白，通过冷冻电子显微照片的三维重建将两个衣壳的结构确定为17埃的分辨率。在这些密度图中，可以清楚地看到组成二聚体的边界，并比较了两个衣壳的四级结构。围绕其二十面体五折轴的二聚体排列几乎是相同的，而二聚体的接近六倍的排列则明显不同。

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