Wounderlich G, Bruss V
Department of Medical Microbiology, University of Göttingen, Federal Republic of Germany.
Arch Virol. 1996;141(7):1191-205. doi: 10.1007/BF01718824.
The small surface protein (S) of the hepatitis B virus (HBV) is synthesized as unglycosylated p24 and N-glycosylated gp27 and forms disulfide linked dimers. Former models proposed that these complexes consist preferentially of p24-gp27 heterodimers. Furthermore, cell free in vitro experiments suggested that p24 has a transmembrane topology different from gp27. We tested these models by expressing the HBV surface proteins in transfected cell cultures and characterizing early maturation products after short pulse labelings. Two dimensional unreduced-reduced polyacrylamide gel electrophoresis demonstrated that p24 and gp27 dimerized without preference for a specific pairing. Protease protection experiments showed that both, p24 and gp27, had identical transmembrane topologies in cell culture. The middle sized (M) and large HBV surface proteins formed mixed dimers with the S protein. Mutant M and S protein in which all 10 cysteine residues in the ectodomain and transmembrane regions were replaced by serine residues formed no intermolecular S-S bridges but were secreted like wild type M and S protein.
乙型肝炎病毒（HBV）的小表面蛋白（S）以未糖基化的p24和N-糖基化的gp27形式合成，并形成二硫键连接的二聚体。以前的模型提出，这些复合物优先由p24-gp27异二聚体组成。此外，无细胞体外实验表明，p24的跨膜拓扑结构与gp27不同。我们通过在转染的细胞培养物中表达HBV表面蛋白并在短脉冲标记后表征早期成熟产物来测试这些模型。二维非还原-还原聚丙烯酰胺凝胶电泳表明，p24和gp27二聚化时对特定配对没有偏好。蛋白酶保护实验表明，在细胞培养中，p24和gp27具有相同的跨膜拓扑结构。中分子（M）和大HBV表面蛋白与S蛋白形成混合二聚体。胞外结构域和跨膜区域中的所有10个半胱氨酸残基都被丝氨酸残基取代的突变型M和S蛋白不形成分子间二硫键，但像野生型M和S蛋白一样分泌。
