The sensor kinase DcuS of Escherichia coli perceives extracellular fumarate by a periplasmic PASP sensor domain. Transmembrane (TM) helix TM2, present as TM2-TM2′ homo-dimer, transmits fumarate activation in a piston-slide across the membrane. The second TM helix of DcuS, TM1, is known to lack piston movement. Structural and functional properties of TM1 were analyzed. Oxidative Cys-crosslinking (CL) revealed homo-dimerization of TM1 over the complete membrane, but only the central part showed α-helical +3/+4 spacing of the CL maxima. The GALLEX bacterial two-hybrid system indicates TM1/TM1′ interaction, and the presence of a TM1-TM1′ homo-dimer is suggested. The peripheral TM1 regions presented CL in a spacing atypical for α-helical arrangement. On the periplasmic side the deviation extended over 11 AA residues (V32-S42) between the α-helical part of TM1 and the onset of PASP. In the V32-S42 region, CL efficiency decreased in the presence of fumarate. Therefore, TM1 exists as a homo-dimer with α-helical arrangement in the central membrane region, and non-α-helical arrangement in the connector to PASP. The fumarate induced structural response in the V32-S42 region is suggested to represent a structural adaptation to the shift of TM2 in the TM1-TM1′/TM2-TM2′ four-helical bundle.

中文翻译：

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大肠杆菌DcuS传感器激酶跨膜螺旋TM1的特性，TM2活塞信号的定子

传感器激酶 DcuS大肠杆菌通过周质 PAS 感知细胞外延胡索酸盐磷传感器域。跨膜 (TM) 螺旋 TM2，以 TM2-TM2' 同源二聚体形式存在，在活塞滑动中跨膜传递延胡索酸活化。DcuS 的第二个 TM 螺旋，TM1，已知缺乏活塞运动。分析了TM1的结构和功能特性。氧化半胱氨酸交联 (CL) 显示 TM1 在整个膜上同源二聚化，但只有中央部分显示 CL 最大值的 α-螺旋 +3/+4 间距。GALLEX 细菌双杂交系统表明 TM1/TM1' 相互作用，并表明存在 TM1-TM1' 同源二聚体。外围 TM1 区域以非典型 α 螺旋排列的间距呈现 CL。在周质侧，TM1 的 α-螺旋部分和 PAS 开始之间的偏差延伸到 11 个 AA 残基 (V32-S42)磷. 在 V32-S42 区域，CL 效率在富马酸盐存在下降低。因此，TM1 以同源二聚体的形式存在，在中心膜区域具有 α-螺旋排列，在 PAS 的连接器中存在非α-螺旋排列磷. V32-S42 区域的富马酸盐诱导的结构反应被认为代表了对 TM1-TM1'/TM2-TM2' 四螺旋束中 TM2 移位的结构适应。