Sensing of cytoplasmic pH by bacterial chemocreceptors involves the linker region that connects the membrane-spanning and the signal-modulating helices
Sensing of cytoplasmic pH by bacterial chemocreceptors involves the linker region that connects the membrane-spanning and the signal-modulating helices
复制标题
DOI：
10.1074/jbc.m109930200
复制
发表时间：
2002-01-11
影响因子：
4.8
通讯作者：
Kawagishi, I
中科院分区：
文献类型：
--
作者：
Umemura, T;Matsumoto, Y;Kawagishi, I
大肠杆菌的两种主要化学感受器Tsr和Tar对细胞质pH（pH（i））的相同变化介导相反的反应。我们着手鉴定参与pH（i）传感的残基，以深入了解化学感受器所采用的信号传导的一般机制。对Tsr和Tar的各种嵌合体的表征将pH敏感区定位于Tar的Arg（259）-His（267）和Tsr的Gly（261）-ASp（269）。Tar的该区域含有三个带电荷的残基（Arg（259）-Ser（261）、Asp（263）和His（267）），其在Tsr中具有相反电荷的对应物（Gly（261）-Glu（262）、Arg（265）和Asp（269））。将Tar或Arg（259）-Ser（260）中的所有三个带电残基单独替换为Tsr的相应残基，逆转了pHi响应的极性，而替换Asp（263）或His（267）不改变极性，但改变了pHi响应的时程。这些结果表明，连接第二跨膜螺旋与第一甲基化螺旋的接头区域内的短胞质区域的静电性质对于在pH传感期间切换化学感受器的信号传导状态是至关重要的。该区域响应于外部配体的类似构象变化可能是跨膜信号传导的关键组分。
The two major chemoreceptors of Escherichia coli, Tsr and Tar, mediate opposite responses to the same changes in cytoplasmic pH (pH(i)). We set out to identify residues involved in pH(i) sensing to gain insight into the general mechanisms of signaling employed by the chemoreceptors. Characterization of various chimeras of Tsr and Tar localized the pH-sensing region to Arg(259)-His(267) of Tar and Gly(261)-ASp(269) of Tsr. This region of Tar contains three charged residues (Arg(259)-Ser(261), Asp(263), and His(267)) that have counterparts of opposite charge in Tsr (Gly(261)-Glu(262), Arg(265), and Asp(269)). The replacement of all of the three charged residues in Tar or Arg(259)-Ser(260) alone by the corresponding residues of Tsr reversed the polarity of pHi response, whereas the replacement of Asp(263) or His(267) did not change the polarity but altered the time course of pHi response. These results suggest that the electrostatic properties of a short cytoplasmic region within the linker region that connects the second transmembrane helix to the first methylation helix is critical for switching the signaling state of the chemoreceptors during pH sensing. Similar conformational changes of this region in response to external ligands may be critical components of transmembrane signaling.