Kim So Young, Yoon Sa Ryong, Han SongI, Yun Yuna, Jung Kwang-Hwan
Department of Life Science and Institute of Biological Interfaces, Sogang University, Shinsu-Dong 1, Mapo-Gu, Seoul, 121-742, Korea.
Mol Microbiol. 2014 Aug;93(3):403-14. doi: 10.1111/mmi.12635. Epub 2014 Jun 30.
In 2003, Anabaena sensory rhodopsin (ASR), a membrane-bound light sensor protein, was discovered in cyanobacteria. Since then, a large number of functions have been described for ASR, based on protein biochemical and biophysical studies. However, no study has determined the in vivo mechanism of photosensory transduction for ASR and its transducer protein (ASRT). Here, we aimed to determine the role of ASRT in physiological photo-regulation. ASRT is known to be related to photochromism, because it regulates the expression of phycocyanin (cpc-gene) and phycoerythrocyanin (pec gene), two major proteins of the phycobilisome in cyanobacteria. By examining wild type and knockout mutant Anabaena cells, we showed that ASRT repressed the expression of these two genes. We also demonstrated physical interactions between ASRT, ASR, and the promoter regions of cpc, pec, kaiABC (circadian clock gene) and the asr operon, both in vitro and in vivo. Binding assays indicated that ASRT had different sites of interaction for binding to ASR and DNA promoter regions. ASRT also influenced the retinal re-isomerization rate in dark through a physical interaction with ASR, and it regulated reporter gene expression in vivo. These results suggested that ASRT relayed the photosignal from ASR and directly regulated gene expression.
2003年，在蓝细菌中发现了一种膜结合光传感器蛋白——鱼腥藻感光视紫红质（ASR）。从那时起，基于蛋白质生化和生物物理研究，人们已经描述了ASR的大量功能。然而，尚未有研究确定ASR及其转导蛋白（ASRT）在体内的光感转导机制。在此，我们旨在确定ASRT在生理光调节中的作用。已知ASRT与光致变色有关，因为它调节蓝细菌中藻胆体的两种主要蛋白质——藻蓝蛋白（cpc基因）和藻红蛋白（pec基因）的表达。通过检测野生型和敲除突变型鱼腥藻细胞，我们发现ASRT抑制了这两个基因的表达。我们还在体外和体内证明了ASRT、ASR与cpc、pec、kaiABC（生物钟基因）和asr操纵子的启动子区域之间存在物理相互作用。结合分析表明，ASRT与ASR和DNA启动子区域结合的相互作用位点不同。ASRT还通过与ASR的物理相互作用影响黑暗中视黄醛的重新异构化速率，并在体内调节报告基因的表达。这些结果表明，ASRT传递来自ASR的光信号并直接调节基因表达。
