Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.
Department of Molecular Structural Biology, Max-Planck-Institute for Biochemistry, Martinsried, Germany.
Structure. 2019 Nov 5;27(11):1634-1646.e3. doi: 10.1016/j.str.2019.09.005. Epub 2019 Oct 3.
Sulfolobus turreted icosahedral virus (STIV) is a model archaeal virus and member of the PRD1-adenovirus lineage. Although STIV employs pyramidal lysis structures to exit the host, knowledge of the viral entry process is lacking. We therefore initiated studies on STIV attachment and entry. Negative stain and cryoelectron micrographs showed virion attachment to pili-like structures emanating from the Sulfolobus host. Tomographic reconstruction and sub-tomogram averaging revealed pili recognition by the STIV C381 turret protein. Specifically, the triple jelly roll structure of C381 determined by X-ray crystallography shows that pilus recognition is mediated by conserved surface residues in the second and third domains. In addition, the STIV petal protein (C557), when present, occludes the pili binding site, suggesting that it functions as a maturation protein. Combined, these results demonstrate a role for the namesake STIV turrets in initial cellular attachment and provide the first molecular model for viral attachment in the archaeal domain of life.
嗜热硫化叶菌十二面体病毒（STIV）是一种模式古菌病毒，属于 PRD1-腺病毒科。尽管 STIV 采用金字塔状的裂解结构来离开宿主，但病毒进入宿主的过程尚不清楚。因此，我们开始研究 STIV 的附着和进入。负染色和冷冻电镜照片显示病毒颗粒附着在源自 Sulfolobus 宿主的类似于菌毛的结构上。断层重建和子断层平均化显示 STIV C381 炮塔蛋白识别菌毛。具体来说，X 射线晶体学确定的 C381 的三链卷曲结构表明，菌毛识别是由第二和第三结构域中保守的表面残基介导的。此外，当存在时，STIV 花瓣蛋白（C557）会封闭菌毛结合位点，表明它作为成熟蛋白发挥作用。综上所述，这些结果表明 STIV 炮塔在初始细胞附着中起作用，并为古菌域生命中病毒附着的第一个分子模型提供了依据。
