Preston V G, al-Kobaisi M F, McDougall I M, Rixon F J
MRC Virology Unit, Institute of Virology, Glasgow, U.K.
J Gen Virol. 1994 Sep;75 ( Pt 9):2355-66. doi: 10.1099/0022-1317-75-9-2355.
The herpes simplex virus type 1 (HSV-1) polypeptides encoded by genes UL26 and UL26.5 are thought to form a scaffold around which the capsid shell assembles. The UL26 gene specifies a proteinase that cleaves both itself and the UL26.5 gene product. To study the structure and function of the UL26 and UL26.5 gene products, the proteins were expressed in cells infected with recombinant baculoviruses containing the genes under the control of the polyhedrin promoter. Both polypeptides were made in large amounts, approaching the levels of polyhedrin protein expressed in wild-type baculovirus. The UL26 polypeptide behaved in a similar manner to the protein made in HSV-1-infected cells, cleaving itself rapidly into the capsid proteins VP21 and VP24 and converting the UL26.5 product more slowly into the capsid protein VP22a. The results of immunoblot analysis using antisera specific for the amino-terminal region of the UL26 polypeptide suggested that both the first and second ATGs in the UL26 open reading frame were recognized as translational start signals but the first ATG was the preferred initiation codon as is the case in HSV-1-infected cells. Electron microscopic examination of thin section preparations of cells infected with both the UL26.5- and UL26-recombinant baculoviruses revealed the presence of large numbers of small spherical particles, often arranged in a semi-crystalline array. These clusters of scaffold-like particles were not present in cells infected with UL26-recombinant baculovirus but were observed occasionally in UL26.5-recombinant baculovirus-infected cells. The results suggest that the proteinase, in the absence of other HSV capsid proteins, stimulates the formation of large numbers of scaffold-like particles present either as semi-crystalline arrays or as dispersed structures.
由基因UL26和UL26.5编码的单纯疱疹病毒1型（HSV-1）多肽被认为形成了一个支架，衣壳围绕该支架组装。UL26基因指定一种蛋白酶，该蛋白酶可切割自身以及UL26.5基因产物。为了研究UL26和UL26.5基因产物的结构和功能，这些蛋白质在感染了含有在多角体蛋白启动子控制下的这些基因的重组杆状病毒的细胞中表达。两种多肽均大量产生，接近野生型杆状病毒中表达的多角体蛋白水平。UL26多肽的行为与在HSV-1感染细胞中产生的蛋白质相似，迅速将自身切割成衣壳蛋白VP21和VP24，并将UL26.5产物更缓慢地转化为衣壳蛋白VP22a。使用针对UL26多肽氨基末端区域的抗血清进行免疫印迹分析的结果表明，UL26开放阅读框中的第一个和第二个ATG均被识别为翻译起始信号，但第一个ATG是首选的起始密码子，这与HSV-1感染细胞中的情况相同。对感染了UL26.5和UL26重组杆状病毒的细胞的超薄切片制备物进行电子显微镜检查，发现存在大量小球形颗粒，这些颗粒通常排列成半结晶阵列。这些支架样颗粒簇不存在于感染了UL26重组杆状病毒的细胞中，但偶尔在感染了UL26.5重组杆状病毒的细胞中观察到。结果表明，在没有其他HSV衣壳蛋白的情况下，蛋白酶会刺激形成大量以半结晶阵列或分散结构形式存在的支架样颗粒。
