Liu F, Roizman B
Marjorie B. Kovler Viral Oncology Laboratories, University of Chicago, Illinois 60637.
J Virol. 1993 Mar;67(3):1300-9. doi: 10.1128/JVI.67.3.1300-1309.1993.
The herpes simplex virus 1 UL26 open reading frame encodes a protease which cleaves a small carboxyl-terminal peptide of itself and its substrate encoded by an overlapping, 3'-coterminal transcriptional unit, designated UL26.5. The translational product of UL26.5 is infected-cell protein 35c,d (ICP35c,d) (F. Liu and B. Roizman, J. Virol. 65:206-212, 1991; F. Liu and B. Roizman, J. Virol. 65:5149-5156, 1991). The protease activity maps at the amino terminus of UL26 translation product designated Pra. Cleavage of Pra to remove the carboxyl-terminal 25 amino acids converts the protein to Prb (F. Liu and B. Roizman, Proc. Natl. Acad. Sci. USA 89:2076-2080, 1992). Other studies reported a second, amino-terminus-proximal cleavage in UL26 gene products made in Escherichia coli (I. C. Deckman, M. Hagen, and P. J. McCann III, J. Virol 66:7362-7367, 1992; C. L. DiIanni, D. A. Drier, I. C. Deckman, P.J. McCann III, F. Liu, B. Roizman, R. J. Colonno, and M. G. Cordingley, J. Biol. Chem., 368:2048-2051, 1993). We report the following results. (i) The amino-terminus-proximal cleavage of UL26 protein in eukaryotic cells generates two polypeptides, an apparent M(r)-25,000 amino-terminal polypeptide designated Prn and a carboxyl-terminal polypeptide which corresponds in electrophoretic mobility to ICP35a. Cleavage of the carboxyl-terminal 25 amino acids by the UL26 protease converted ICP35a to ICP35b. (ii) Replacement of Ala-247-Ser-248 with Arg-Pro precluded the amino-terminus-proximal cleavage. (iii) Prn, the amino-terminal product of the cleavage reaction at amino acid 247 functions as a protease. (iv) Additional amino acid substitutions in the putative domain of the protease yielded results consistent with the hypothesis that UL26 encodes a serine protease. (v) The domain of the UL26 protein whose modification confers the formation of double bands for all products (Pra, Prb, ICP35a, ICP35b, ICP35c,d, and ICP35e,f) except Prn maps in the domain shared by UL26 and UL26.5, between codons 307 and 417.
单纯疱疹病毒1型UL26开放阅读框编码一种蛋白酶，该蛋白酶可切割其自身以及由一个重叠的3'共末端转录单元（称为UL26.5）编码的底物的小羧基末端肽。UL26.5的翻译产物是感染细胞蛋白35c、d（ICP35c、d）（F. 刘和B. 罗伊兹曼，《病毒学杂志》65:206 - 212，1991；F. 刘和B. 罗伊兹曼，《病毒学杂志》65:5149 - 5156，1991）。蛋白酶活性定位于UL26翻译产物的氨基末端，称为Pra。Pra经切割去除羧基末端的25个氨基酸后转化为Prb（F. 刘和B. 罗伊兹曼，《美国国家科学院院刊》89:2076 - 2080，1992）。其他研究报道在大肠杆菌中产生的UL26基因产物存在另一种靠近氨基末端的切割（I. C. 德克曼、M. 哈根和P. J. 麦肯三世，《病毒学杂志》66:7362 - 7367，1992；C. L. 迪兰尼、D. A. 德里尔、I. C. 德克曼、P. J. 麦肯三世、F. 刘、B. 罗伊兹曼、R. J. 科隆诺和M. G. 科丁利，《生物化学杂志》368:2048 - 2051，1993）。我们报告以下结果。（i）真核细胞中UL26蛋白靠近氨基末端的切割产生两种多肽，一种表观分子量为25,000的氨基末端多肽，称为Prn，以及一种羧基末端多肽，其电泳迁移率与ICP35a相对应。UL26蛋白酶切割羧基末端的25个氨基酸后，ICP35a转化为ICP35b。（ii）将Ala - 247 - Ser - 248替换为Arg - Pro可阻止靠近氨基末端的切割。（iii）Prn是氨基酸247处切割反应的氨基末端产物，具有蛋白酶功能。（iv）在蛋白酶的假定结构域中进行的其他氨基酸替换产生的结果与UL26编码丝氨酸蛋白酶的假设一致。（v）UL26蛋白的一个结构域，其修饰会使除Prn之外的所有产物（Pra、Prb、ICP35a、ICP35b、ICP35c、d和ICP35e、f）形成两条带，该结构域位于UL26和UL26.5共有的结构域中，在密码子307和417之间。
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