Ligand Binding and Signaling State of Anabaena Sensory Rhodopsin Transducer

 描述（由申请人提供）：与离子泵细菌视紫红质同系物不同，微生物感觉视紫红质-转导分子复合物是探索信号级联中蛋白质-蛋白质相互作用化学的关键范例。在2003年，淡水蓝藻鱼腥藻（念珠藻）sp. PCC 7120揭示了一个染色体基因编码的感觉视紫红质类似物。与盐古菌感觉视紫红质相反，它不含任何膜转导基因产物。然而，相邻的基因产物被指示为该感光体的可溶性转导分子。光活化受体介导的信号传导的详细分子机制尚不清楚。所提出的模型是不相关的任何已知的微生物感官为基础的“趋光性”。然而，它类似于视觉光感受器、视紫红质和经由细胞质组分的其他G蛋白偶联信号传导。因此，这种可溶性推定的转导蛋白的作用可能建立一个新的模式的信号共享的盐古菌和真核生物。有趣的是，这种假定的可溶性转导分子存在于一系列不含感觉性视紫红质光感受器的微生物物种中。序列和结构折叠同源性揭示了这种分子没有任何既定的功能特征。基因组数据库搜索显示它们存在于广泛的微生物群体中，包括各种病原体。存在于其他序列中的换能器的同源序列被称为“未识别功能域”[DUF]家族。该科包括病原体，如滋养菌属、放线菌属和嗜热裂菌属。光感受器和推定的换能器的原子分辨率结构是可用的。基于结构基序的生物信息学分析表明，该基因可能属于微生物小分子碳水化合物结合结构域超家族的一员。它很可能是一种新型的碳水化合物结合模块在一个独特的β夹心框架。我们的初步数据，基于单极定位，表明强相关性和亲和力的细菌纤维素合成蛋白，具体定位在极点。最近的核磁共振研究表明，这种换能器与DNA的真核生物样的相互作用。此外，基于序列的分析预测沿着来自PI工作的初始数据支持转导蛋白的磷接受性质。此外，磷酸化导致损害的不寻常的稳定性的转换器，这表明其在信号转导中的假定的作用。这种推定的转导蛋白的不寻常的稳定组装及其分离将阐明这种信号传导状态。 DUF蛋白分子。本项目的目的是将作为磷受体模块的换能器的功能状态与糖结合基序的存在相关联，并表征这种特征对受体结合的调节。转导子信号状态的表征将拓宽我们对其他DUF成员包括各种病原体的理解。

 DESCRIPTION (provided by applicant): Unlike to ion pump bacteriorhodopsin homologues, microbial sensory rhodopsin-transducer molecular complexes served a key paradigm for exploring the chemistry of protein-protein interaction in signaling cascade. In 2003, freshwater cyanobacterium Anabaena (Nostoc) sp. PCC 7120 revealed a chromosomal gene encoding a sensory rhodopsin analogue. In contrast to haloarchaeal sensory rhodopsin, it does not contain any membrane transducer gene product. However, an adjacent gene product is indicated to be a soluble transducer molecule for this photoreceptor. The detailed molecular mechanism of photoactivated receptor mediated signaling is not known. The proposed model is not related to any known microbial sensory based "phototaxis". However, it is analogous to visual photoreceptor, rhodopsin and to other G- protein coupled signaling via cytoplasmic components. Thus the role of this soluble putative transducer protein may establish a novel mode of signaling as shared by haloarchaea and eukarya. Interestingly, this putative soluble transducer molecule is present in a series of microbial species that do not contain sensory rhodopisn photoreceptor. Sequential and structural fold homology reveals such molecule without any established functional feature. Genome database search revealed their presence in broad microbial population including various pathogens. The homologue sequence of a transducer present in other sequences is referred to as "domain of unidentified function" [DUF], family. This family includes pathogens, such as Tropheryma, Actinomyces and Thermobifida. The atomic resolution structures of both photoreceptor and putative transducer are available. Structural motif based bioinformatics analysis has revealed that the transducer homologue may be classified as a member of a super family of microbial small carbohydrate binding domain. It is likely that it may serve as a novel carbohydrate binding module in a unique beta sandwich framework. Our preliminary data, based on unipolar localization suggests strong correlation and affinity to bacterial cellulose synthesis proteins that specifically localizes at pole. Recent NMR study has shown a eukaryotic like interaction of this transducer with DNA. Further, sequence- based analysis prediction along with initial data from PI's work supports the phosphor-accepting property of the transducer protein. Additionally, the phosphorylation leads to impair the unusual stability of transducer, suggesting its putative role in signaling. The unusual stable assembly and its segregation of this putative transducer protein would elucidate the signaling state of this DUF protein molecule. This project is aimed to relate the functional state of transducer as a phosphor-acceptor module and presence of a sugar binding motif and characterize the modulation of such a feature on receptor binding. The characterization of transducer's signaling state would broaden our understanding towards other DUF members including various pathogens as well.