Vanslyke J K, Whitehead S S, Wilson E M, Hruby D E
Department of Microbiology, Oregon State University, Corvallis 97331-3804.
Virology. 1991 Aug;183(2):467-78. doi: 10.1016/0042-6822(91)90976-i.
The most abundant vaccinia virus (VV) core protein found within the virion is protein 4a, which represents approximately 14% of the particle's dry weight. The 4a protein is synthesized as a 102.5-kDa precursor, which is proteolytically processed to a 62-kDa product concomitant with virion assembly. To identify the pathway by which P4a is converted into 4a, immunological reagents which are specific for subregions of the P4a precursor were developed and used in concert with peptide mapping and protein sequencing procedures. The results obtained suggest that the 891 amino acid P4a precursor is cleaved at two locations, between residues 614 and 615 and 697 and 698. Both the large amino-terminal 4a protein (residues 1-614) and the carboxy-terminal-derived 23-kDa protein (residues 698-891) become major virion constituents. The location and fate of the small internal peptide (residues 615-697) is not known. Interestingly, an analysis of the predicted amino acid sequences at the sites of cleavage within the P4a precursor indicated the presence of an Ala-Gly decreases Thr motif flanking the 697-698 site and an Ala-Gly decreases Ser motif flanking the 614-615 site. Since both of these signals are quite similar to the Ala-Gly decreases Ala signal previously identified as the cleavage point within the VV P4b and P25K core protein precursors (VanSlyke et al., 1991.J. Gen. Virol. 72, 411-416), this suggests that processing of all three core protein precursors may be coordinately linked and/or catalyzed by the same proteinase during viral assembly.
在痘苗病毒（VV）病毒粒子中发现的最丰富的核心蛋白是蛋白4a，它约占病毒粒子干重的14%。4a蛋白最初合成时是一个102.5 kDa的前体，在病毒粒子组装过程中经蛋白水解加工成为一个62 kDa的产物。为了确定P4a转化为4a的途径，针对P4a前体不同亚区域开发了特异性免疫试剂，并与肽图谱分析和蛋白质测序方法协同使用。所得结果表明，891个氨基酸的P4a前体在两个位置被切割，分别在第614和615位氨基酸残基之间以及第697和698位氨基酸残基之间。较大的氨基末端4a蛋白（第1 - 614位氨基酸残基）和羧基末端衍生的23 kDa蛋白（第698 - 891位氨基酸残基）都成为病毒粒子的主要成分。内部小肽（第615 - 697位氨基酸残基）的位置和去向尚不清楚。有趣的是，对P4a前体切割位点处预测氨基酸序列的分析表明，在697 - 698位点两侧存在一个Ala - Gly↓Thr基序，在614 - 615位点两侧存在一个Ala - Gly↓Ser基序。由于这两个信号与先前确定为痘苗病毒P4b和P25K核心蛋白前体切割点的Ala - Gly↓Ala信号非常相似（VanSlyke等人，1991年。《普通病毒学杂志》72卷，411 - 416页），这表明在病毒组装过程中，所有三种核心蛋白前体的加工可能由同一种蛋白酶协同连接和/或催化。
