Constitutive signaling by the phototaxis receptor sensory rhodopsin II from disruption of its protonated Schiff base Asp-73 interhelical salt bridge
Constitutive signaling by the phototaxis receptor sensory rhodopsin II from disruption of its protonated Schiff base Asp-73 interhelical salt bridge
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DOI：
10.1073/pnas.94.10.4960
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发表时间：
1997-05-13
影响因子：
11.1
通讯作者：
Spudich, JL
中科院分区：
文献类型：
--
作者：
Spudich, EN;Zhang, WS;Spudich, JL
感觉视紫红质II（Sensory Rhodopsin II，SRII）是古细菌盐杆菌（Halobacterium salinarum）中的一种排斥性趋光性受体，其七螺旋结构类似于视觉色素，并且通过螺旋G中的质子化席夫碱将视网膜与蛋白质连接，天冬氨酸光谱分析表明，螺旋C中的73与未光解的SRII中的质子化席夫碱是抗衡的，并且在光转化过程中是席夫碱的质子受体与受体信号传导状态相比，编码突变的SRII（Asn取代Asp-73（D 73 N））和SRII转换器HtrII的基因在盐生H. salinarum细胞中的共表达导致3倍更高的游泳逆转频率，伴随着HtrII在黑暗中的去甲基化，这表明D 73 N SRII在其非光刺激状态下产生驱避信号，类似的组成性信号传导已显示通过人视杆视紫红质中席夫碱抗衡物和质子受体Glu-113的类似中性残基取代产生，对这两种七螺旋受体的解释是，野生型蛋白质的光激活主要是由光异构化引起的-因此，通过光活性位点中的螺旋C-G盐桥破坏的受体活化是跨越古细菌和人类之间巨大进化距离的亚视黄基蛋白质中的一般机制。
Sensory rhodopsin II (SRII) is a repellent phototaxis receptor in the archaeon Halobacterium salinarum, similar to visual pigments in its seven-helix structure and linkage of retinal to the protein by a protonated Schiff base in helix G, Asp-73 in helix C is shown by spectroscopic analysis to be a counterion to the protonated Schiff base in the unphotolyzed SRII and to be the proton acceptor from the Schiff base during photoconversion to the receptor signaling state, Coexpression of the genes encoding mutated SRII with Asn substituted for Asp-73 (D73N) and the SRII transducer HtrII in H, salinarum cells results in a 3-fold higher swimming reversal frequency accompanied by demethylation of HtrII in the dark, showing that D73N SRII produces repellent signals in its unphotostimulated state, Analogous constitutive signaling has been shown to be produced by the similar neutral residue substitution of the Schiff base counterion and proton acceptor Glu-113 in human rod rhodopsin, The interpretation for both seven-helix receptors is that light activation of the wild-type protein is caused primarily by photoisomerization-induced transfer of the Schiff base proton on helix G to its primary carboxylate counterion on helix C, Therefore receptor activation by helix C-G salt-bridge disruption in the photoactive site is a general mechanism in retinylidene proteins spanning the vast evolutionary distance between archaea and humans.