Locher K P, Rees B, Koebnik R, Mitschler A, Moulinier L, Rosenbusch J P, Moras D
Department of Microbiology, Biozentrum, University of Basel, Switzerland.
Cell. 1998 Dec 11;95(6):771-8. doi: 10.1016/s0092-8674(00)81700-6.
FhuA protein facilitates ligand-gated transport of ferrichrome-bound iron across Escherichia coli outer membranes. X-ray analysis at 2.7 A resolution reveals two distinct conformations in the presence and absence of ferrichrome. The monomeric protein consists of a hollow, 22-stranded, antiparallel beta barrel (residues 160-714), which is obstructed by a plug (residues 19-159). The binding site of ferrichrome, an aromatic pocket near the cell surface, undergoes minor changes upon association with the ligand. These are propagated and amplified across the plug, eventually resulting in substantially different protein conformations at the periplasmic face. Our findings reveal the mechanism of signal transmission and suggest how the energy-transducing TonB complex senses ligand binding.
FhuA蛋白促进了铁载体结合铁通过大肠杆菌外膜的配体门控运输。2.7埃分辨率的X射线分析揭示了在有和没有铁载体存在时两种不同的构象。单体蛋白由一个中空的、22股反平行β桶（残基160 - 714）组成，该桶被一个塞子（残基19 - 159）阻塞。铁载体的结合位点，即细胞表面附近的一个芳香口袋，在与配体结合时发生微小变化。这些变化通过塞子传播并放大，最终导致周质面的蛋白质构象有显著不同。我们的研究结果揭示了信号传递机制，并提出了能量转换型TonB复合物如何感知配体结合。
