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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structure of FliM provides insight into assembly of the switch complex in the bacterial flagella motor
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Structure of FliM provides insight into assembly of the switch complex in the bacterial flagella motor

机译：FliM的结构可深入了解细菌鞭毛马达中开关复合体的组装

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摘要

Bacteria switch the direction their flagella rotate to control movement. FliM, along with FIN and FliG, compose a complex in the motor that, upon binding phosphorylated CheY, reverses the sense of flagellar rotation. The 2.0-angstrom resolution structure of the FIN middle domain (FliM(M)) from Thermotoga maritima reveals a pseudo-2-fold symmetric topology similar to the CheY phosphatases CheC and CheX. A variable structural element, which, in CheC, mediates binding to CheD (alpha 2') and, in CheX, mediates dimerization (beta(x)'), has a truncated structure unique to FIN (alpha(2)'). An exposed helix of FliM(M) (alpha 1) does not contain the catalytic residues of CheC and CheX but does include positions conserved in FIN sequences. Cross-linking experiments with site-directed cysteine mutants show that FIN self-associates through residues on alpha(1) and alpha(2)'. CheY activated by BeF3- binds to FIN with approximate to 40-fold higher affinity than CheY (K-d = 0.04 mu M vs. 2 mu M). Mapping residue conservation, suppressor mutation sites, binding data, and deletion analysis onto the FliM(M) surface defines regions important for contacts with the stator-interacting protein FliG and for either counterclockwise or clockwise rotation. Association of 33-35 FliM subunits would generate a 44- to 45-nm-diameter disk, consistent with the known dimensions of the C-ring. The localization of counterclockwise- and clockwise-biasing mutations to distinct surfaces suggests that the binding of phosphorylated CheY cooperatively realigns FIN around the ring.
机译：细菌切换鞭毛旋转的方向以控制运动。 FliM与FIN和FliG一起构成了马达中的复合物，结合了磷酸化的CheY后，该复合物逆转了鞭毛旋转的感觉。滨海嗜热菌的FIN中间结构域（FliM（M））的2.0埃分辨率结构揭示了类似于CheY磷酸酶CheC和CheX的伪2倍对称拓扑。可变结构元件，在CheC中，介导与CheD（alpha 2'）的结合，在CheX中，介导二聚化（beta（x）'），具有FIN特有的截短结构（alpha（2）'）。 FliM（M）（α1）的暴露螺旋不包含CheC和CheX的催化残基，但包含FIN序列中保守的位置。定点半胱氨酸突变体的交联实验表明，FIN通过alpha（1）和alpha（2）'上的残基自缔合。被BeF3-激活的CheY与FIN结合的亲和力比CheY高约40倍（K-d = 0.04μMvs. 2μM）。映射残基保守性，抑制突变位点，绑定数据，和删除分析到FliM（M）表面上，定义了对于与定子相互作用蛋白FliG接触以及逆时针或顺时针旋转很重要的区域。结合33-35个FliM亚基将生成直径为44-45 nm的圆盘，这与C环的已知尺寸一致。逆时针和顺时针偏向突变在不同表面的定位表明磷酸化的CheY的结合可协同重新排列环周围的FIN。

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