Chang C, Mooser A, Plückthun A, Wlodawer A
Macromolecular Crystallography Laboratory, NCI, National Institutes of Health, Frederick, Maryland 21702, USA.
J Biol Chem. 2001 Jul 20;276(29):27535-40. doi: 10.1074/jbc.M102778200. Epub 2001 Apr 27.
The TonB-dependent complex of Gram-negative bacteria couples the inner membrane proton motive force to the active transport of iron.siderophore and vitamin B(12) across the outer membrane. The structural basis of that process has not been described so far in full detail. The crystal structure of the C-terminal domain of TonB from Escherichia coli has now been solved by multiwavelength anomalous diffraction and refined at 1.55-A resolution, providing the first evidence that this region of TonB (residues 164-239) dimerizes. Moreover, the structure shows a novel architecture that has no structural homologs among any known proteins. The dimer of the C-terminal domain of TonB is cylinder-shaped with a length of 65 A and a diameter of 25 A. Each monomer contains three beta strands and a single alpha helix. The two monomers are intertwined with each other, and all six beta-strands of the dimer make a large antiparallel beta-sheet. We propose a plausible model of binding of TonB to FhuA and FepA, two TonB-dependent outer-membrane receptors.
革兰氏阴性菌的TonB依赖性复合物将内膜质子动力与铁、铁载体和维生素B12跨外膜的主动运输偶联起来。到目前为止，该过程的结构基础尚未得到全面详细的描述。现在，通过多波长反常衍射解析了来自大肠杆菌的TonB C端结构域的晶体结构，并在1.55埃分辨率下进行了精修，首次证明TonB的该区域（第164至239位氨基酸残基）会形成二聚体。此外，该结构显示出一种新颖的架构，在任何已知蛋白质中都没有结构同源物。TonB C端结构域的二聚体呈圆柱形，长度为65埃，直径为25埃。每个单体包含三条β链和一个α螺旋。两个单体相互缠绕，二聚体的所有六条β链形成一个大的反平行β折叠片。我们提出了一个关于TonB与FhuA和FepA（两种TonB依赖性外膜受体）结合的合理模型。
