Armstrong D J, Roman A
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis 46202-5120.
J Gen Virol. 1992 May;73 ( Pt 5):1275-9. doi: 10.1099/0022-1317-73-5-1275.
The E7 open reading frames of human papillomavirus type 6 (HPV-6) and HPV-16 encode proteins consisting of 98 amino acids that are quite similar in sequence yet different in electrophoretic mobility. Moreover, these proteins vary strikingly in oncogenicity. To investigate the molecular basis of the differences in structure and function, site-directed mutagenesis was used to exchange non-conserved amino acid residues between the two proteins. The mutated coding regions were expressed as fusion proteins in Escherichia coli and identified by Western blotting. Comparative analysis of the affinity-purified mutated E7 fusion proteins in polyacrylamide slab mini-gels in the presence of SDS and 2-mercaptoethanol revealed altered electrophoretic mobilities. This analysis suggests that the aspartic acid at residue 4 (Asp 4) contributes to the characteristic aberrant migration of the HPV-16 E7 protein in SDS-polyacrylamide gels.
人乳头瘤病毒6型（HPV-6）和HPV-16的E7开放阅读框编码由98个氨基酸组成的蛋白质，这些蛋白质在序列上非常相似，但电泳迁移率不同。此外，这些蛋白质在致癌性方面有显著差异。为了研究结构和功能差异的分子基础，采用定点诱变技术在两种蛋白质之间交换非保守氨基酸残基。突变的编码区在大肠杆菌中表达为融合蛋白，并通过蛋白质免疫印迹法进行鉴定。在SDS和2-巯基乙醇存在的情况下，在聚丙烯酰胺平板微型凝胶中对亲和纯化的突变E7融合蛋白进行比较分析，结果显示电泳迁移率发生了改变。该分析表明，第4位残基的天冬氨酸（Asp 4）有助于HPV-16 E7蛋白在SDS-聚丙烯酰胺凝胶中呈现出特征性的异常迁移。
