Institute of Complex Systems (ICS), ICS-5: Molecular Biophysics, Research Centre Juelich, 52425 Juelich, Germany.
J Photochem Photobiol B. 2013 Jun 5;123:55-8. doi: 10.1016/j.jphotobiol.2013.03.008. Epub 2013 Mar 29.
The complex of sensory rhodopsin II (NpSRII) with its cognate transducer (NpHtrII) mediates negative phototaxis in halobacteria Natronomonas pharaonis. Upon light activation NpSRII triggers, by means of NpHtrII, a signal transduction chain homologous to the two component system in eubacterial chemotaxis. Here we report on the crystal structure of the ground state of the mutant NpSRII-D75N/NpHtrII complex in the space group I212121. Mutations of this aspartic acid in light-driven proton pumps dramatically modify or/and inhibit protein functions. However, in vivo studies show that the similar D75N mutation retains functionality of the NpSRII/NpHtrII complex. The structure provides the molecular basis for the explanation of the unexpected observation that the wild and the mutant complexes display identical physiological response on light excitation.
感光视紫红质 II 复合物（NpSRII）与其同源转导蛋白（NpHtrII）介导嗜盐古菌盐沼盐杆菌的负趋光性。在光激活后，NpSRII 通过 NpHtrII 触发与真细菌趋化性中的双组分系统同源的信号转导链。本文报道了在空间群 I212121 中突变型 NpSRII-D75N/NpHtrII 复合物的基态晶体结构。在光驱动质子泵中，这种天冬氨酸的突变极大地改变或/和抑制了蛋白质的功能。然而，体内研究表明，类似的 D75N 突变保留了 NpSRII/NpHtrII 复合物的功能。该结构为解释这一意外观察结果提供了分子基础，即野生型和突变型复合物在光激发下表现出相同的生理反应。
