Changing the direction of flagellar rotation in bacteria by modulating the ratio between the rotational states of the switch protein FliM.
Changing the direction of flagellar rotation in bacteria by modulating the ratio between the rotational states of the switch protein FliM.
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通过调节开关蛋白 FliM 旋转状态之间的比率来改变细菌鞭毛旋转的方向。
DOI：
10.1006/jmbi.2001.4992
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发表时间：
2001
影响因子：
5.6
通讯作者：
M. Eisenbach
中科院分区：
文献类型：
--
作者：
A. Bren;M. Eisenbach
细菌趋化性的主要问题之一是控制鞭毛旋转方向的开关如何发挥作用。已经确定的是，信号分子CheY与开关蛋白FliM的结合将旋转从默认方向（逆时针）转变为顺时针。这种转变是如何完成的仍然是一个谜。我们在这项研究中的目的是确定FliM分子在顺时针状态（即被CheY占据）的分数与顺时针旋转的概率之间的相关性。为了这个目的，我们逐渐表达，从质粒中，顺时针FliM突变体蛋白在细胞中表达，从染色体，野生型FliM，但没有趋化蛋白。我们验证了质粒携带的FliM在开关中交换染色体FliM。令人惊讶的是，在开关中的大多数FliM分子是顺时针分子之前，没有获得实质性的顺时针概率。此后，顺时针概率的上升非常陡峭。这些结果表明，顺时针概率的增加需要高水平的FliM占用CheY约P.他们进一步表明，在顺时针旋转急剧增加后，增加CheY水平，在几项研究中报道，是由于，至少部分地，在开关内的结合后相互作用的协同性。我们还进行了反向实验，其中野生型FliM在顺时针fliM突变体的背景下逐渐表达。在这种情况下，建立一定顺时针概率所需的顺时针突变蛋白质的水平低于原始实验。如果我们的系统（其中开关中FliM的旋转状态之间的比率是通过缓慢交换建立的）和本机系统（其中该比率是通过FliM占用的快速变化建立的）是可比的，则结果表明，滞后涉及开关功能。这种情况可能反映了一种阻尼机制，这种机制可以防止CheY磷酸化水平的波动将开关从一个方向转向另一个方向。
One of the major questions in bacterial chemotaxis is how the switch, which controls the direction of flagellar rotation, functions. It is well established that binding of the signaling molecule CheY to the switch protein FliM shifts the rotation from the default direction, counterclockwise, to clockwise. How this shift is done is still a mystery. Our aim in this study was to determine the correlation between the fraction of FliM molecules in the clockwise state (i.e. occupied by CheY) and the probability of clockwise rotation. For this purpose we gradually expressed, from a plasmid, a clockwise FliM mutant protein in cells that express, from the chromosome, wild-type FliM but no chemotaxis proteins. We verified that plasmid-borne FliM exchanges chromosomal FliM in the switch. Surprisingly, a substantial clockwise probability was not obtained before the large majority of the FliM molecules in the switch were clockwise molecules. Thereafter, the rise in clockwise probability was very steep. These results suggest that an increase in the clockwise probability requires a high level of FliM occupancy by CheY approximately P. They further suggest that the steep increase in clockwise rotation upon increasing CheY levels, reported in several studies, is due, at least in part, to cooperativity of post-binding interactions within the switch. We also carried out the inverse experiment, in which wild-type FliM was gradually expressed in a background of a clockwise fliM mutant. In this case, the level of the clockwise mutant protein, required for establishing a certain clockwise probability, was lower than in the original experiment. If our system (in which the ratio between the rotational states of FliM in the switch is established by slow exchange) and the native system (in which the ratio is established by fast changes in FliM occupancy) are comparable, the results suggest that hysteresis is involved in the switch function. Such a situation might reflect a damping mechanism, which prevents a situation in which fluctuations in the phosphorylation level of CheY throw the switch from one direction of rotation to the other.
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影响因子：
5.6
作者：
Zhao,R;Schuster,SC;Khan,S
通讯作者：
Khan,S
DOI：
10.1073/pnas.96.18.10134
发表时间：
1999-08
影响因子：
11.1
作者：
Dennis R. Thomas;David G.A. Morgan;D. DeRosier
通讯作者：
Dennis R. Thomas;David G.A. Morgan;D. DeRosier
影响因子：
5.6
作者：
FRANCIS, NR;SOSINSKY, GE;DEROSIER, DJ
通讯作者：
DEROSIER, DJ
DOI：
10.1073/pnas.94.15.8168
发表时间：
1997-07-22
影响因子：
11.1
作者：
Siegele, DA;Hu, JC
通讯作者：
Hu, JC
DOI：
10.1073/pnas.94.14.7263
发表时间：
1997-07-08
影响因子：
11.1
作者：
Spiro, PA;Parkinson, JS;Othmer, HG
通讯作者：
Othmer, HG