The mechanism of signal transduction in photoreceptors

光感受器信号转导机制

• 批准号: 6933920
• 负责人: HARTMUT LUECKE
• 金额: $ 26.03万
• 依托单位: UNIVERSITY OF CALIFORNIA-IRVINE
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2007-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6933920
• 关键词: X ray crystallography; conformation; cryoscience; crystallization; phosphorylation; photoactivation; photosynthetic bacteria; protein isoforms; protein protein interaction; protein structure function; rhodopsin; structural biology; visual photoreceptor; visual phototransduction

DESCRIPTION (provided by applicant): Signal reception and signal transduction constitute fundamental processes by which living cells perceive and ultimately react to external stimuli such as light, chemicals (nutrients, toxins, hormones), heat and mechanical signals. Most signal receptors reside in the cytoplasmic membrane that separates the inside of a cell from the external medium. Primary receptors for light (photoreceptors) are the basis of all forms of vision where the energy from absorbed single photons is used to bring about a conformational change in the chromophore, usually the isomerization of a double bond within picoseconds. On a slower timescale, the surrounding protein and water matrix responds to the conformational change of the chromophore and ultimately results in conformational and electrostatic changes that are sensed by a transducer molecule. Microbial rhodopsins are a family of photoactive, seven-transmembrane helix, retinylidene proteins found in phylogenetically diverse microorganisms, including haloarchaea, proteobacteria, cyanobacteria, fungi, and algae. Sensory rhodopsins I and II (SRI and SRII) in haloarchaea, Chlamydomonas rhodopsins CsoA and CsoB, and Anabaena rhodopsin, are photosensory receptors, spectrally tuned throughout the visible spectrum to relay information to the cell regarding the intensity and color of light in the environment. SRI and SRII are sensors for phototaxis in Hatobacterium salinarum and related halophilic archaea. SRI mediates attractant motility responses to green-orange wavelengths used by the ion pumps BR and HR, while SRII mediates blue-light avoidance responses. The SRI and SRII proteins are subunits of multicomponent signaling complexes and relay signals by protein-protein interaction to integral membrane transducer proteins (HtrI and HtrII, respectively) that control a cytoplasmic phosphorylation pathway that modulates the cell's motility apparatus. In order to elucidate the basis of spectral tuning of the photoreceptor sensory rhodopsin (SRII) and to obtain a detailed structure-based mechanism of how light-induced conformational changes trigger signaling in its cognate transducer (HtrII) we will 1. Determine the structure of the single-site mutant R72A, a residue recently implicated in spectral tuning. 2, Determine the crystal structure of the photoreceptor in the long-lived (O) signaling state and identify the main signaling components by comparing it to the recently solved ground state structure. 3, Compare the crystal structure of the 9-TM helical SRII/HtrlI fusion construct in the off-state with that of the photoactivated signaling state, In order to determine the atomic structure and the photoactivation mechanism of the recently identified Anabaena photoreceptor and its soluble putative transducer we will 4. Determine the crystal structure of the soluble putative transducer, a 14-kDa protein on the same operon as the photoreceptor with no sequence homology to any known protein. 5. Determine the crystal structure of the primary Anabaena photoreceptor in the ground and signaling state. 6. Determine the structure of the complex of the Anabaena photoreceptor with its putative transducer.

描述（由申请人提供）：信号接收和信号转导构成了活细胞感知并最终对外部刺激（如光、化学物质（营养物质、毒素、激素）、热和机械信号）做出反应的基本过程。大多数信号受体位于细胞质膜上，细胞质膜将细胞内部与外部介质隔开。光的主要感受器（光感受器）是所有视觉形式的基础，其中吸收的单光子的能量用于引起发色团的构象变化，通常是在皮秒内双键的异构化。在较慢的时间尺度上，周围的蛋白质和水基质对发色团的构象变化做出反应，并最终导致由传感器分子感知的构象和静电变化。微生物紫红质是一类具有光活性的七跨膜螺旋视黄嘌呤蛋白，存在于系统发育多样的微生物中，包括盐古菌、变形菌、蓝藻菌、真菌和藻类。感觉视紫红质I和II （SRI和SRII）在盐古菌、衣藻视紫红质CsoA和CsoB以及水藻视紫红质中是光感觉受体，在整个可见光谱中进行光谱调谐，将有关环境中光的强度和颜色的信息传递给细胞。SRI和SRII是盐酸Hatobacterium salinarum和相关的嗜盐古细菌的趋光传感器。SRI介导对离子泵BR和HR使用的绿橙波长的引诱剂运动反应，而SRII介导蓝光回避反应。SRI和SRII蛋白是多组分信号复合物的亚基，并通过蛋白与整体膜换能器蛋白（分别为HtrI和HtrII）的相互作用传递信号，后者控制细胞质磷酸化途径，调节细胞的运动装置。为了阐明光感受器感觉视紫红质（SRII）光谱调谐的基础，并获得光诱导构象变化如何触发其同源换能器（HtrII）信号传导的详细结构机制，我们将1。确定单位点突变体R72A的结构，这是最近与光谱调谐有关的残基。2、确定光感受器在长寿命(O)信号状态下的晶体结构，并将其与最近解决的基态结构进行比较，确定主要的信号成分。3、比较9-TM螺旋SRII/ htli融合结构在关闭状态和光激活信号状态下的晶体结构，以确定最近发现的水仙鱼光感受器及其可溶换能器的原子结构和光激活机制。测定可溶性换能器的晶体结构，这是一个与光感受器在同一操纵子上的14 kda蛋白质，与任何已知蛋白质没有序列同源性。5. 确定在地面和信号状态下的原始水仙光感受器的晶体结构。6. 确定水仙鱼光感受器及其假定的换能器的复合物的结构。