Membrane segment organization in the stator complex of the flagellar motor: implications for proton flow and proton-induced conformational change.
Membrane segment organization in the stator complex of the flagellar motor: implications for proton flow and proton-induced conformational change.
复制标题
DOI：
10.1021/bi801347a
复制
发表时间：
2008-10-28
期刊：
影响因子：
2.9
通讯作者：
Blair, David F.
中科院分区：
文献类型：
--
作者：
Kim, Eun A.;Price-Carter, Marian;Carlquist, William C.;Blair, David F.
MotA和MotB是构成细菌鞭毛马达定子的膜蛋白。每个马达包含若干个MotA4MotB2复合物，它们独立发挥作用，使质子穿过膜，并将质子流与旋转耦合起来。旋转的机制尚未详细了解，但据认为涉及由MotB的一个关键天冬氨酸残基（大肠杆菌蛋白质中的天冬氨酸32）处的质子结合/解离驱动的定子复合物的构象变化。MotA有4个跨膜区段，MotB有1个。先前使用靶向二硫键交联的研究表明，两个MotB亚基的跨膜区段在复合物中心聚集在一起，被4个MotA亚基的TM3和TM4区段环绕。在此，交联研究扩展到MotA的TM1和TM2，使用在这些区段的几个位置引入的半胱氨酸残基。所观察到的二硫键交联模式表明，TM2区段位于同一亚基的TM3和TM4区段之间，在那里它可能对结构中形成质子通道的部分有贡献。TM1位于其自身亚基的TM4和另一个亚基的TM3区段之间的界面处，在那里它可能稳定复合物。基于交联结果的一个结构模型显示了从周质到MotB区段内端附近的天冬氨酸32残基的畅通路径。该模型表明某些保守的、具有重要功能的残基彼此接近。这些结果被用于建立一个关于质子诱导的定子构象变化的明确模型。
MotA and MotB are membrane proteins that form the stator of the bacterial flagellar motor. Each motor contains several MotA4MotB2 complexes, which function independently to conduct protons across the membrane and couple proton flow to rotation. The mechanism of rotation is not understood in detail but is thought to involve conformational changes in the stator complexes driven by proton association/dissociation at a critical Asp residue of MotB (Asp 32 in the protein of Escherichia coli). MotA has four membrane segments and MotB has one. Previous studies using targeted disulfide crosslinking showed that the membrane segments of the two MotB subunits are together at the center of the complex, surrounded by the TM3 and TM4 segments of the four MotA subunits. Here, the cross-linking studies are extended to TM1 and TM2 of MotA, using Cys residues introduced in several positions in the segments. The observed patterns of disulfide cross-linking indicate that the TM2 segment is positioned between segments TM3 and TM4 of the same subunit, where it could contribute to the proton-channel-forming part of the structure. TM1 is at the interface between TM4 of its own subunit and the TM3 segment of another subunit, where it could stabilize the complex. A structural model based on the cross-linking results shows unobstructed pathways reaching from the periplasm to the Asp 32 residues near the inner ends of the MotB segments. The model indicates a close proximity for certain conserved, functionally important residues. The results are used to develop an explicit model for the proton-induced conformational change in the stator.
登录
查看更多内容
影响因子：
64.8
作者：
LOWE, G;MEISTER, M;BERG, HC
通讯作者：
BERG, HC
DOI：
10.1073/pnas.0509932103
发表时间：
2006-05-23
影响因子：
11.1
作者：
Reid, Stuart W.;Leake, Mark C.;Berry, Richard M.
通讯作者：
Berry, Richard M.
影响因子：
64.8
作者：
BLOCK, SM;BERG, HC
通讯作者：
BERG, HC
DOI：
10.1073/pnas.83.4.917
发表时间：
1986-02-01
影响因子：
11.1
作者：
BRANDL, CJ;DEBER, CM
通讯作者：
DEBER, CM
影响因子：
2.9
作者：
Braun, TF;Al-Mawsawi, LQ;Blair, DF
通讯作者：
Blair, DF