Studies of phytochromes and signal transductbn pathways in cyanobacterial phototaxis

克隆了一种新的黄素结合蛋白基因，并在大肠杆菌中表达。蛋白在2.0 A下结晶并溶解。新的光敏色素样基因pixA被认为是一种具有正趋光性的光感受器。由nixB和nixC编码的调节蛋白是通过组合诱变假设的。鉴定出运动菌毛组装所需的调节基因为：pilG、pilH、pill、pilJ、pill - n和pill - c。后两个基因分别在染色体上不同的位点上表达。从Synechocystis sp. PCC 6803中分离到正向趋光受体PixJ1蛋白。分离得到的蛋白在蓝光和绿光区表现出新的吸收光谱和差异光谱。PixJ1的发色团为藻蓝胆素衍生物。四种新的黄素结合光感受器蛋白异种表达，并对其光周期进行了部分表征。采用生物信息学和生化分析方法对丝状蓝藻Anabaena sp. pcc7120的PAS结构域蛋白进行了系统的研究。毛亚基的基因被系统地破坏，鉴定为pil9、pi110和pil11。

A gene for a novel flavin-binding protein that is involved in positive phototaxis was cloned from T. elongatus and expressed in E. coli, and expressed. The protein was crystallized and resolved at 2.0 A.Novel phytochrome-like gene pixA was identified as a putative photoreceptor for positive phototaxis. Regulator proteins encoded by nixB and nixC are hypothesized by combinatorial mutagenesis.Regulator genes essential for assembly of motility pili were identified as follows : pilG, pilH, pill, pilJ, pilL-N and pilL-C. The latter two genes were separately expressed on distinct loci on the chromosome.Positive phototaxis photoreceptor PixJ1 protein was isolated from Synechocystis sp. PCC 6803. The protein thus isolated showed novel absorption spectra and difference spectrum in blue and green light regions. The chromophore of PixJ1 was concluded to be a derivative of phycocyanobilin.Four novel flavin-binding photoreceptor proteins were expressed heterologously and their photocycles were partially characterized.The PAS domain proteins of a filamentous cyanobacterium Anabaena sp. PCC 7120 were systematically studied by bioinformatics and biochemical analyses.Genes for the pili subunits were systematically disrupted and identified as pil9,pi110, and pil11.