Sapp M, Volpers C, Müller M, Streeck R E
Institute of Medical Microbiology, University of Mainz, Germany.
J Gen Virol. 1995 Sep;76 ( Pt 9):2407-12. doi: 10.1099/0022-1317-76-9-2407.
The organization of the major (L1) and minor (L2) proteins in the human papillomavirus capsid is still largely unknown. In this study we analysed the disulphide bonding between L1 proteins and the association of L2 proteins with capsomers using virus-like particles obtained in insect cells by co-expression of the L1 and L2 genes of human papillomavirus type 33. About 50% of the L1 protein molecules in these particles (1.29 g/cm3) formed disulphide-bonded trimers. Reduction of the intermolecular disulphide bonds by dithiotreitol (DTT) treatment caused disassembly of virus-like particles into capsomers. This indicates that disulphide bonds between capsomers at the threefold symmetry positions of the capsid are essential for the assembly of the papillomavirus capsid. In contrast, the L2 protein was not engaged in intermolecular disulphide bonding. The L2 protein remained associated with capsomers on disassembly by treatment with DTT. When the disassembly was carried out in 0.65 M-NaCl, complete L2 protein molecules bound preferentially to capsomer oligomers, whereas truncated L2 protein molecules bound only to monomers. In 0.15 M-NaCl only complete L2 protein molecules remained bound to capsomers. This indicates that different regions of the L2 protein molecule are differentially involved in the association of the papillomavirus capsid.
人乳头瘤病毒衣壳中主要（L1）和次要（L2）蛋白的组织方式在很大程度上仍不清楚。在本研究中，我们利用人乳头瘤病毒33型的L1和L2基因在昆虫细胞中共表达获得的病毒样颗粒，分析了L1蛋白之间的二硫键结合以及L2蛋白与衣壳粒的缔合情况。这些颗粒（密度为1.29 g/cm³）中约50%的L1蛋白分子形成了二硫键连接的三聚体。用二硫苏糖醇（DTT）处理还原分子间二硫键会导致病毒样颗粒解聚成衣壳粒。这表明衣壳三重对称位置处衣壳粒之间的二硫键对于乳头瘤病毒衣壳的组装至关重要。相比之下，L2蛋白未参与分子间二硫键结合。经DTT处理解聚后，L2蛋白仍与衣壳粒缔合。当在0.65 M NaCl中进行解聚时完整的L2蛋白分子优先与衣壳粒寡聚体结合，而截短的L2蛋白分子仅与单体结合。在0.15 M NaCl中，只有完整的L2蛋白分子仍与衣壳粒结合。这表明L2蛋白分子的不同区域在乳头瘤病毒衣壳缔合过程中发挥不同作用。
