Role of a conserved prolyl residue (Pro173) of MotA in the mechanochemical reaction cycle of the proton-driven flagellar motor of Salmonella.
Role of a conserved prolyl residue (Pro173) of MotA in the mechanochemical reaction cycle of the proton-driven flagellar motor of Salmonella.
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MotA 的保守脯氨酰残基 (Pro173) 在沙门氏菌质子驱动鞭毛马达的机械化学反应循环中的作用。
DOI：
10.1016/j.jmb.2009.08.022
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发表时间：
2009
影响因子：
5.6
通讯作者：
K. Namba
中科院分区：
文献类型：
--
作者：
Shuichi Nakamura;Yusuke V. Morimoto;N. Kami‐ike;T. Minamino;K. Namba
MoTA/B复合体作为质子驱动的细菌鞭毛马达的定子。通过定子复合体的质子传输与定子-转子相互作用产生的扭矩有效地耦合在一起。在鼠伤寒沙门氏菌中，MOTA的高度保守的Pro173残基与MOTB的绝对保守的Asp33残基非常接近，后者被认为是一个质子结合部位。Pro173被认为参与了质子流入与扭矩产生之间的耦合。然而，目前还不清楚Pro173执行什么关键功能。在这里，我们表征了沙门氏菌慢运动mota(P173A)突变体的鞭毛马达的运动性和扭矩-速度关系。突变电机产生的失速扭矩处于野生型水平，表明电机中的定子数量和转子-定子相互作用都不受P173A替代的影响。与此相一致的是，MOTA(P173A)等位基因对野生型的运动有很强的显性-负性效应。相比之下，低负荷下的高速旋转明显受到突变的影响，这表明扭矩产生周期的最大速率受到严重限制。用一个简单的动力学模型对扭矩-速度曲线的模拟表明，该突变降低了MoTA/B复合体的构象变化速度，从而减缓了机械力化学反应周期。基于这些结果，我们认为Pro173在促进质子快速转移和扭矩产生循环的定子复合体的构象动力学中起着重要作用。
The MotA/B complex acts as the stator of the proton-driven bacterial flagellar motor. Proton translocation through the stator complex is efficiently coupled with torque generation by the stator–rotor interactions. In Salmonella enterica serovar Typhimurium, the highly conserved Pro173 residue of MotA is close to the absolutely conserved Asp33 residue of MotB, which is believed to be a proton-binding site. Pro173 is postulated to be involved in coupling proton influx to torque generation. However, it remains unknown what critical function Pro173 carries out. Here, we characterize the motility and the torque–speed relation of the flagellar motor of the slow motile motA(P173A) mutant of Salmonella. Stall torque produced by the mutant motor was at the wild-type level, indicating that neither the number of stators in the motor nor the rotor–stator interaction is affected by the P173A substitution. In agreement with this, the motA(P173A) allele exerted a strong dominant-negative effect on wild-type motility. In contrast, high-speed rotation at low load was significantly impaired by the mutation, suggesting that the maximum rate of torque generation cycle is severely limited. Simulation of the torque–speed curve by a simple kinetic model indicated that the mutation reduces the rate of conformational changes of the MotA/B complex that switches the exposure of Asp33 to the outside and the inside of the cell, thereby slowing down the mechanochemical reaction cycle. Based on these results, we propose that Pro173 plays an important role in facilitating the conformational dynamics of the stator complex for rapid proton translocation and torque generation cycle.
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影响因子：
2.9
作者：
Braun, TF;Al-Mawsawi, LQ;Blair, DF
通讯作者：
Blair, DF
MotA 胞质结构域的残基对于细菌鞭毛运动中扭矩的产生至关重要。
DOI：
10.1006/jmbi.1997.1316
发表时间：
1997
期刊：
Journal of molecular biology.
影响因子：
--
作者：
Zhou,J;Blair,DF
通讯作者：
Blair,DF
DOI：
10.1073/pnas.95.11.6436
发表时间：
1998-05
影响因子：
11.1
作者：
Jiadong Zhou;S. A. Lloyd;D. Blair
通讯作者：
Jiadong Zhou;S. A. Lloyd;D. Blair
影响因子：
3.4
作者：
Chen, XB;Berg, HC
通讯作者：
Berg, HC
影响因子：
2.9
作者：
Kojima, S;Blair, DF
通讯作者：
Blair, DF