Bowman Brian R, Welschhans Robert L, Jayaram Hariharan, Stow Nigel D, Preston Valerie G, Quiocho Florante A
Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
J Virol. 2006 Mar;80(5):2309-17. doi: 10.1128/JVI.80.5.2309-2317.2006.
Herpesviruses replicate their double stranded DNA genomes as high-molecular-weight concatemers which are subsequently cleaved into unit-length genomes by a complex mechanism that is tightly coupled to DNA insertion into a preformed capsid structure, the procapsid. The herpes simplex virus type 1 UL25 protein is incorporated into the capsid during DNA packaging, and previous studies of a null mutant have demonstrated that its function is essential at the late stages of the head-filling process, either to allow packaging to proceed to completion or for retention of the viral genome within the capsid. We have expressed and purified an N-terminally truncated form of the 580-residue UL25 protein and have determined the crystallographic structure of the region corresponding to amino acids 134 to 580 at 2.1-Angstroms resolution. This structure, the first for any herpesvirus protein involved in processing and packaging of viral DNA, reveals a novel fold, a distinctive electrostatic distribution, and a unique "flexible" architecture in which numerous flexible loops emanate from a stable core. Evolutionary trace analysis of UL25 and its homologues in other herpesviruses was used to locate potentially important amino acids on the surface of the protein, leading to the identification of four putative docking regions for protein partners.
疱疹病毒将其双链DNA基因组复制为高分子量串联体，随后通过一种与DNA插入预先形成的衣壳结构（原衣壳）紧密偶联的复杂机制，将其切割成单位长度的基因组。单纯疱疹病毒1型UL25蛋白在DNA包装过程中被整合到衣壳中，之前对一个缺失突变体的研究表明，其功能在头部填充过程的后期至关重要，要么是为了使包装过程得以完成，要么是为了将病毒基因组保留在衣壳内。我们表达并纯化了580个残基的UL25蛋白的N端截短形式，并以2.1埃的分辨率确定了对应于氨基酸134至580区域的晶体结构。该结构是涉及病毒DNA加工和包装的任何疱疹病毒蛋白的首个结构，揭示了一种新颖的折叠、独特的静电分布以及一种独特的“柔性”结构，其中许多柔性环从稳定的核心发出。对UL25及其在其他疱疹病毒中的同源物进行进化追踪分析，以定位该蛋白表面潜在的重要氨基酸，从而鉴定出四个假定的蛋白伴侣对接区域。
