Killmann H, Braun V
Universität Tübingen, Germany.
FEMS Microbiol Lett. 1998 Apr 1;161(1):59-67. doi: 10.1111/j.1574-6968.1998.tb12929.x.
The FhuA protein of Escherichia coli K-12 transports ferrichrome and the structurally related antibiotic albomycin across the outer membrane and serves as a receptor for the phages T1, T5, and phi 80 and for colicin M. In this paper, we show that chimeric proteins consisting of the central part of FhuA and the N- and C-terminal parts of FhuE (coprogen receptor) or the N- and/or C-terminal parts of FoxA (ferrioxamine B receptor), function as ferrichrome transport proteins. Although the hybrid proteins contained the previously identified gating loop of FhuA, which is the principal binding site of the phages T5, T1, and phi 80, only the hybrid protein consisting of the N-terminal third of FoxA and the C-terminal two thirds of FhuA conferred weak phage sensitivity to cells. Apparently, the gating loop is essential, but not sufficient for wild-type levels of ferrichrome transport and for phage sensitivity. The properties of FhuA-FoxA hybrids suggest different regions of the two receptors for ferric siderophore uptake.
大肠杆菌K-12的FhuA蛋白可将高铁色素和结构相关抗生素阿波霉素转运穿过外膜，并作为噬菌体T1、T5和φ80以及大肠菌素M的受体。在本文中，我们表明，由FhuA的中央部分与FhuE（粪卟啉原受体）的N端和C端部分或FoxA（铁胺B受体）的N端和/或C端部分组成的嵌合蛋白，可作为高铁色素转运蛋白发挥作用。尽管杂合蛋白包含先前鉴定出的FhuA门控环，该门控环是噬菌体T5、T1和φ80的主要结合位点，但只有由FoxA的N端三分之一和FhuA的C端三分之二组成的杂合蛋白赋予细胞较弱的噬菌体敏感性。显然，门控环对于野生型水平的高铁色素转运和噬菌体敏感性至关重要，但并不充分。FhuA-FoxA杂合体的特性表明，这两种铁载体摄取受体的不同区域发挥了作用。
