Francis N R, Sosinsky G E, Thomas D, DeRosier D J
Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02254-9110.
J Mol Biol. 1994 Jan 28;235(4):1261-70. doi: 10.1006/jmbi.1994.1079.
A putative complex of the three switch proteins, FliG, FliM and FliN appears to be directly involved in torque generation and control of direction of rotation. We have developed a preparative procedure for flagellar motors that retains these proteins as evidenced by Western blots using anti-FliG, anti-FliM and anti-FliN antibodies. Immunogold labeling with these three antibodies shows that the three switch proteins are localized to the motor. Electron micrographs of frozen-hydrated preparations reveal a large, new component we have termed the "C ring complex" attached to the cytoplasmic face of the M ring. In a three-dimensional reconstruction of the cylindrically averaged structure, the M-S ring complex appears thicker and wider by the addition of extra material to the cytoplasmic surface of the M ring. In addition, extending into the cytoplasm from the thickened M ring is the C ring complex, a thin-walled cylinder having a length of 170 A and an outer diameter of 450 A compared to the 290 A diameter of the M ring. We provide evidence that the thickened M ring contains FliG and that the C ring complex may contain FliM and FliN. The large diameter of the C ring complex may permit interaction with the M ring and with the circlet of studs thought to be the MotA/MotB complex.
由三种开关蛋白FliG、FliM和FliN组成的假定复合体似乎直接参与扭矩产生和旋转方向控制。我们已经开发出一种用于鞭毛马达的制备方法，该方法能保留这些蛋白，使用抗FliG、抗FliM和抗FliN抗体进行蛋白质免疫印迹可证明这一点。用这三种抗体进行免疫金标记显示，这三种开关蛋白定位于马达。冷冻水合制剂的电子显微镜照片显示出一个大的新组分，我们将其称为“C环复合体”，它附着在M环的胞质面上。在圆柱平均结构的三维重建中，M-S环复合体由于在M环的胞质表面添加了额外物质而显得更厚更宽。此外，从增厚的M环延伸到细胞质中的是C环复合体，这是一个薄壁圆柱体，长度为170埃，外径为450埃，而M环的直径为290埃。我们提供的证据表明，增厚的M环含有FliG，而C环复合体可能含有FliM和FliN。C环复合体的大直径可能允许其与M环以及被认为是MotA/MotB复合体的螺柱环相互作用。
