Bruss Volker
Department of Virology, University of Göttingen, Kreuzbergring 57, 37075 Göttingen, Germany.
Virus Res. 2004 Dec;106(2):199-209. doi: 10.1016/j.virusres.2004.08.016.
The hepatitis B virus (HBV) is an enveloped DNA virus with an icosahedral capsid replicating via reverse transcription. The crystal structure of the capsid is known. It has a diameter of 36 nm and is formed by one protein species (C protein). The viral envelope contains three different coterminal proteins (S, M, and L proteins) spanning the membrane several times. These proteins are not only released from infected cells as components of the viral envelope but in 10,000-fold excess as subviral lipoprotein particles with a diameter of 22 nm containing no capsid. Assembly of the capsid occurs in the cytosol and results in packaging of a 3.5 kb RNA molecule together with viral and cellular factors. This newly formed capsid cannot be enveloped. Rather, synthesis of the viral DNA genome in the lumen of the capsid by reverse transcription is required to induce a budding competent state. Envelopment then takes place at an intracellular membrane of the pre-Golgi compartment. The S and the L protein, but not the M protein, is required for this process. The L protein forms two different transmembrane topologies. The isoform exposing the N-terminal part at the cytosolic side of the membrane is essential for budding. In this domain, a 22 amino acid (aa) long linear stretch has been mapped genetically to play a vital role in the morphogenetic process. This domain probably mediates the contact to the capsid. A second matrix domain was mapped to the cytosolic loop of the S protein. A similar genetic approach identified two small areas on the capsid surface, which might interact with the envelope proteins during envelopment.
乙型肝炎病毒（HBV）是一种具有二十面体衣壳的包膜DNA病毒，通过逆转录进行复制。衣壳的晶体结构已知。它的直径为36纳米，由一种蛋白质（C蛋白）形成。病毒包膜包含三种不同的共末端蛋白（S、M和L蛋白），它们多次跨越膜。这些蛋白不仅作为病毒包膜的成分从受感染细胞中释放出来，而且还以直径为22纳米、不含衣壳的亚病毒脂蛋白颗粒形式过量释放，其数量是前者的10000倍。衣壳在细胞质中组装，导致一个3.5 kb的RNA分子与病毒和细胞因子一起被包装。这个新形成的衣壳不能被包膜。相反，需要通过在衣壳腔内逆转录合成病毒DNA基因组来诱导出芽能力状态。然后在高尔基体前区室的细胞内膜处发生包膜过程。这个过程需要S蛋白和L蛋白，但不需要M蛋白。L蛋白形成两种不同的跨膜拓扑结构。在膜的胞质侧暴露N末端部分的异构体对于出芽至关重要。在这个结构域中，一个22个氨基酸长的线性片段已通过遗传学方法定位，在形态发生过程中起关键作用。这个结构域可能介导与衣壳的接触。第二个基质结构域定位在S蛋白的胞质环上。类似的遗传学方法在衣壳表面确定了两个小区域，它们可能在包膜过程中与包膜蛋白相互作用。
