Physikalische Biochemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Golm, Germany.
Biochem Soc Trans. 2010 Oct;38(5):1386-9. doi: 10.1042/BST0381386.
TSPs (tailspike proteins) are essential infection organelles of bacteriophage P22. Upon infection, P22TSP binds to and cleaves the O-antigen moiety of the LPS (lipopolysaccharide) of its Salmonella host. To elucidate the role of TSP during infection, we have studied binding to oligosaccharides and polysaccharides of Salmonella enterica Typhimurium and Enteritidis in vitro. P22TSP is a trimeric β-helical protein with a carbohydrate-binding site on each subunit. Octasaccharide O-antigen fragments bind to P22TSP with micromolar dissociation constants. Moreover, P22TSP is an endorhamnosidase and cleaves the host O-antigen. Catalytic residues lie at the periphery of the high-affinity binding site, which enables unproductive binding modes, resulting in slow hydrolysis. However, the role of this hydrolysis function during infection remains unclear. Binding of polysaccharide to P22TSP is of high avidity with slow dissociation rates when compared with oligosaccharides. In vivo, the infection of Salmonella with phage P22 can be completely inhibited by the addition of LPS, indicating that binding of phage to its host via TSP is an essential step for infection.
尾丝蛋白（TSPs）是噬菌体 P22 的必需感染器官。在感染过程中，P22TSP 与沙门氏菌 LPS（脂多糖）的 O-抗原部分结合并切割。为了阐明 TSP 在感染过程中的作用，我们已经在体外研究了与沙门氏菌肠炎 Typhimurium 和肠炎 Enteritidis 的寡糖和多糖的结合。P22TSP 是一种三聚体β-螺旋蛋白，每个亚基上都有一个碳水化合物结合位点。八糖 O-抗原片段与 P22TSP 的解离常数为微摩尔级。此外，P22TSP 是一种内切岩藻糖酶，可切割宿主的 O-抗原。催化残基位于高亲和力结合位点的外围，这使得非生产性结合模式成为可能，从而导致水解缓慢。然而，在感染过程中，这种水解功能的作用仍不清楚。与寡糖相比，多糖与 P22TSP 的结合具有高亲和力和缓慢的解离速率。在体内，噬菌体 P22 对沙门氏菌的感染可以通过 LPS 的添加完全抑制，表明噬菌体通过 TSP 与其宿主的结合是感染的一个必要步骤。
