Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210, USA.
Nat Struct Mol Biol. 2007 Dec;14(12):1221-6. doi: 10.1038/nsmb1317.
Bacteriophage P22 infects Salmonella enterica by injecting its genetic material through the cell envelope. During infection, a specialized tail needle, gp26, is injected into the host, likely piercing a hole in the host cell envelope. The 2.1-Å crystal structure of gp26 reveals a 240-Å elongated protein fiber formed by two trimeric coiled-coil domains interrupted by a triple β-helix.The N terminus of gp26 plugs the portal protein channel, retaining the genetic material inside the virion. The C-terminal tip of the fiber exposes β-hairpins with hydrophobic tips similar to those seen in class II fusion peptides. The α-helical core connecting these two functionally polarized tips presents four trimerization octads with consensus sequence IXXLXXXV. The slender conformation of the gp26 fiber minimizes the surface exposed to solvent, which is consistent with the idea that gp26 traverses the cell envelope lipid bilayers.
噬菌体 P22 通过穿过细胞包膜将其遗传物质注入沙门氏菌中进行感染。在感染过程中，一种特殊的尾部针，即 gp26，被注入宿主，可能在宿主细胞包膜上穿孔。gp26 的 2.1Å 晶体结构揭示了由两个三聚体卷曲螺旋域中断的 240Å 长的蛋白质纤维，该纤维由三重β-螺旋组成。gp26 的 N 端堵塞了门户蛋白通道，将遗传物质保留在病毒体内。纤维的 C 末端尖端暴露了带有疏水性尖端的β发夹，类似于在 II 类融合肽中看到的那些。连接这两个功能极化尖端的α螺旋核心呈现出四个具有共识序列 IXXLXXXV 的三聚体八聚体。gp26 纤维的细长构象使暴露于溶剂的表面积最小化，这与 gp26 穿过细胞包膜脂质双层的想法一致。
