Molecular and behavioral studies on signal transducing mechanisms of photomovement responses in microorganisms

在此期间，对微生物的各种蓝/蓝-绿光感受器光迁移系统进行了研究，得到了以下新的结果：(1)首次发现鞭毛藻Euglena的降温和升光反应的调控系统受外源铵离子的控制。氨离子特异性地增加了降级的畏光细胞的比例，而氨同化抑制剂L-蛋氨酸-DL-亚磺胺则特异性地增加了细胞悬液中降级的畏光细胞的比例。这使我们能够独立地测量升压和降压反应的真实作用光谱。结果表明，这两种反应是由含有黄素的光感受器介导的，具有略有不同的光谱特征。(2)尽管已有报道表明，衣藻的光运动反应受体几乎没有同源…对于考古菌视紫红质，我们的模拟重建研究揭示了衣藻光感受器和嗜盐细菌视紫红质之间视网膜结合部位的高度相似的立体化学结构。虽然这可能表明衣藻中未知的光运动受体与恐怖紫质具有很高的同源性，但我们初步将这一结果归因于蓝绿敏感光感受器进化的可能趋同，这与多种光感受器物种介导各种微生物对蓝/蓝绿光的光运动反应的证据相一致。(3)PYP是真细菌中唯一的光感受器之一。我们测量了含有PYP的盐生外硫杆菌的趋光反应，发现其作用光谱与PYP的吸收光谱相吻合。(4)克隆了一个可能介导盐生外硫螺菌的厌光反应的转导子样蛋白。(5)从澳大利亚盐湖的一种盐生细菌中克隆了一个新的磷紫质成员。(6)在大肠杆菌中表达了磷紫质蛋白，并通过组氨酸标签对重组蛋白进行了纯化。较少

During the period, the following new results were established as to various blue/blue-green photoreceptor-containing photomovement systems of microorganisms.(1)The regulation system of the step-down and the step-up photophobic responses in the flagellate alga Euglena was for the first time revealed to be controlled by exogenous ammonium ion. Ammonium ion specifically increases the fraction of the step-down photophobically cells, whereas L-methionine-DL-sulfoximine, an inhibitor of ammonium assimilation, specifically increases the fraction of step-up photophobically responding cells in a cell suspension. This allowed us to measure independently the true action spectra for both step-up and step-down responses. The results suggested that the two responses are mediated by flavin-containing photoreceptors, having slightly different spectroscopic characters.(2)Despite the reported fact that the receptors for photomovement responses of unicellular green alga Chlamydomonas has little homology … More to archaebacterial rhodopsins, our analog-reconstitution study has revealed a highly similar stereochemical architecture along the retinal binding site between the chlamydomons photoreceptor and halobacterial phoborhodopsin. Though this may suggest a possibility for unidentified photomovement receptor in Chlamydomonas having high homology to phoborhodopsin, we tentatively ascribed the result to a possible convergence in the evolution of blue-green sensitive photoreceptors, This is in accord with several lines of evidence that a wide variety of photoreceptor species mediates photomovement responses of various microorganisms to blue/blue-green light.(3)PYP is one of the unique photoreceptors in eubacteria. We measured step-up photophobic response of Ectothiorhodospira halophila, containing PYP, and found that the action spectrum coincided with the absorption spectrum of PYP.(4)A putative transducer-like protein mediating photophobic response of Ectothiorhodospira halophila has been cloned.(5)A new member of phoborhodopsin was cloned from a halobacterial species from Australian salt lake.(6)Phoborhodopsin from Natronobacteriurm pharaonis has been expressed in E.coil, and the recombinant protein is satisfactory purified by histidine tagging. Less