Microbiology and Wine Research, Institute for Molecular Physiology, Johannes Gutenberg University Mainz, BZ II, Hanns-Dieter-Hüsch-Weg 17, D-55128 Mainz, Germany.
Biol Chem. 2021 Aug 6;402(10):1239-1246. doi: 10.1515/hsz-2021-0254. Print 2021 Sep 27.
The sensor kinase DcuS of perceives extracellular fumarate by a periplasmic PAS 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 PAS. 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 PAS. 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.
感知细胞外延胡索酸盐的传感器激酶 DcuS 通过周质 PAS 传感器结构域实现。跨膜（TM）螺旋 TM2 以 TM2-TM2'同源二聚体的形式存在，在跨膜活塞滑动中传递延胡索酸盐的激活信号。DcuS 的第二个 TM 螺旋 TM1 已知不存在活塞运动。对 TM1 的结构和功能特性进行了分析。氧化半胱氨酸交联（CL）揭示了 TM1 在整个膜上的同源二聚化，但只有中央部分显示出 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，并且存在 TM1-TM1'同源二聚体。周质 TM1 区域的 CL 间距呈现出非典型的α-螺旋排列。在周质侧，α-螺旋 TM1 的部分与 PAS 起始之间的 CL 偏离延伸了超过 11 个氨基酸残基（V32-S42）。在 V32-S42 区域，CL 效率在延胡索酸盐存在的情况下降低。因此，TM1 以中央膜区域的α-螺旋排列和与 PAS 连接的非α-螺旋排列存在同源二聚体。推测延胡索酸盐诱导 V32-S42 区域的结构响应代表了 TM2 在 TM1-TM1'/TM2-TM2'四螺旋束中移位的结构适应。
