A Photochromic Histidine Kinase Rhodopsin (HKR1) That Is Bimodally Switched by Ultraviolet and Blue Light
A Photochromic Histidine Kinase Rhodopsin (HKR1) That Is Bimodally Switched by Ultraviolet and Blue Light
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DOI：
10.1074/jbc.m112.401604
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发表时间：
2012-11-16
影响因子：
4.8
通讯作者：
Hegemann, Peter
中科院分区：
文献类型：
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作者：
Luck, Meike;Mathes, Tilo;Hegemann, Peter
视紫红质是光激活的色蛋白，通过传导蛋白介导信号过程，或通过离子泵或直接光激活通道促进主动或被动离子运输。在这里，我们提供光谱表征的紫质从衣藻眼斑。它属于一个最近发现的，但迄今尚未表征的组氨酸激酶视紫红质（HKRs）家族。这些模块蛋白由视紫红质、组氨酸激酶、反应调节因子以及在某些情况下的效应域（如腺苷酸或鸟苷酸环化酶）组成，它们都以双组分系统的形式编码在单个蛋白中。HKR1的重组视紫红质片段Rh是一个UVA受体（λ (max) = 380 nm），被紫外光转化为稳定的蓝光吸收态Rh- bl （λ (max) = 490 nm）。蓝光将Rh-Bl转化回Rh-UV。拉曼光谱显示，Rh-UV发色团呈不寻常的13-顺，15-反构型，这解释了为什么发色团是去质子化的。Rh-UV的激发态寿命异常稳定，可能是由于相对非极性的视网膜结合袋，在大约100ps内转化为光产物，而蓝色形式的反应速度要快100倍。我们提出光致变色的HKR1在UVA光存在下的行为反应的适应中起作用。
Rhodopsins are light-activated chromoproteins that mediate signaling processes via transducer proteins or promote active or passive ion transport as ion pumps or directly light-activated channels. Here, we provide spectroscopic characterization of a rhodopsin from the Chlamydomonas eyespot. It belongs to a recently discovered but so far uncharacterized family of histidine kinase rhodopsins (HKRs). These are modular proteins consisting of rhodopsin, a histidine kinase, a response regulator, and in some cases an effector domain such as an adenylyl or guanylyl cyclase, all encoded in a single protein as a two-component system. The recombinant rhodopsin fragment, Rh, of HKR1 is a UVA receptor (lambda(max) = 380 nm) that is photoconverted by UV light into a stable blue light-absorbing meta state Rh-Bl (lambda(max) = 490 nm). Rh-Bl is converted back to Rh-UV by blue light. Raman spectroscopy revealed that the Rh-UV chromophore is in an unusual 13-cis, 15-anti configuration, which explains why the chromophore is deprotonated. The excited state lifetime of Rh-UV is exceptionally stable, probably caused by a relatively unpolar retinal binding pocket, converting into the photoproduct within about 100 ps, whereas the blue form reacts 100 times faster. We propose that the photochromic HKR1 plays a role in the adaptation of behavioral responses in the presence of UVA light.