Kenney J M, von Bonsdorff C H, Nassal M, Fuller S D
Structural Biology Programme, EMBL, Heidelberg, Germany.
Structure. 1995 Oct 15;3(10):1009-19. doi: 10.1016/s0969-2126(01)00237-4.
Hepatitis B virus is a major human pathogen which has been extensively studied, yet its structure is unknown. Cryo-electron microscopy of the viral cores expressed in Escherichia coli or isolated from infected liver provides a means for determining the structure of the hepatitis B nucleocapsid.
Using cryo-electron microscopy and three-dimensional image reconstruction, we have determined the structures of duck and human hepatitis B virus cores and find that they have similar dimer-clustered T = 3 and T = 4 icosahedral organizations. The duck virus core protein sequence differs from the human in both length and amino acid content; however, the only significant structural differences observed are the lobes of density on the lateral edges of the projecting (distal) domain of the core protein dimer. The different cores contain varying amounts of nucleic acid, but exhibit similar contacts between the core protein and the nucleic acid. Immunoelectron microscopy of intact cores has localized two epitopes on the core surface corresponding to residues 76-84 and 129-132.
The bacterial expression system faithfully reproduces the native hepatitis B virus core structure even in the absence of the complete viral genome. This confirms that proper assembly of the core is independent of genome packaging. Difference imaging and antibody binding map three sequence positions in the structure: the C terminus and the regions near amino acids 80 and 130. Finally, we suggest that the genome-core interactions and the base (proximal) domain of the core dimer are evolutionarily conserved whereas the projecting domain, which interacts with the envelope proteins, is more variable.
乙型肝炎病毒是一种已被广泛研究的主要人类病原体，但其结构尚不清楚。对在大肠杆菌中表达或从受感染肝脏中分离出的病毒核心进行冷冻电子显微镜观察，为确定乙型肝炎核衣壳的结构提供了一种方法。
利用冷冻电子显微镜和三维图像重建技术，我们确定了鸭乙型肝炎病毒和人乙型肝炎病毒核心的结构，发现它们具有相似的二聚体聚集的T = 3和T = 4二十面体结构。鸭病毒核心蛋白序列在长度和氨基酸含量上与人的不同；然而，观察到的唯一显著结构差异是核心蛋白二聚体突出（远端）结构域侧边缘上的密度叶。不同的核心含有不同量的核酸，但在核心蛋白与核酸之间表现出相似的接触。完整核心的免疫电子显微镜观察已将两个表位定位在核心表面，对应于残基76 - 84和129 - 132。
即使在没有完整病毒基因组的情况下，细菌表达系统也能忠实地再现天然乙型肝炎病毒核心结构。这证实了核心的正确组装与基因组包装无关。差异成像和抗体结合确定了结构中的三个序列位置：C末端以及氨基酸80和130附近的区域。最后，我们认为基因组与核心的相互作用以及核心二聚体的基部（近端）结构域在进化上是保守的，而与包膜蛋白相互作用的突出结构域则更具变异性。
