Starter Grant: Biliprotein Function in the Photomorphogenetic Responses of Fremyella diplosiphon (Microbial Biology Starter Grant)

蓝细菌和其他光合生物具有微调对波动光照的反应的能力。蓝细菌在其光合捕光天线复合体中含有吸收光的藻胆蛋白，称为藻胆体。一些蓝藻具有改变藻胆体中藻胆蛋白的组成和浓度的能力，以响应光环境的变化。 这种能力被称为互补色适应，它本身由感光胆蛋白RcaE控制。来自蓝藻Fremyella diplosiphon的RcaE对绿色和红色光都有响应。最近的研究表明，在体内，RcaE需要一个酶的蛋白质伴侣的共价连接的发色团的保守的半胱氨酸残基。本研究的长期目标是确定由RcaE控制的光调节信号转导级联。尽管在理解互补色适应的分子基础方面取得了进展，但对RcaE活性的光调节机制的理解是不完整的。该项目的具体目标如下：（i）负责生色团与RcaE共价连接的裂解酶将通过构建和筛选适当的表达文库来鉴定，（ii）细菌表达系统将用于分离生色团化的RcaE，以及（iii）由RcaE启动的光调控的复杂磷酸化级联反应将进一步表征。这项研究的一个更广泛的影响是发展本科科学专业和学生的能力，他们来自代表性不足的群体，参加密歇根州立大学的植物科学计划本科研究人员进行分析和批判性思考。

Cyanobacteria and other photosynthetic organisms possess the ability to finely tune responses to fluctuating illumination. Cyanobacteria contain light-absorbing phycobiliproteins in their photosynthetic light-harvesting antenna complexes, called phycobilisomes. Some cyanobacteria possess the ability to alter the composition and concentrations of the phycobiliproteins contained in their phycobilisomes in response to changes in the photoenvironment. This capacity, called complementary chromatic adaptation, is itself controlled by a photosensory biliprotein, RcaE. RcaE from the cyanobacterium Fremyella diplosiphon is responsive to both green and red light. Recent studies suggest that, in vivo, RcaE requires an enzymatic protein partner for the covalent attachment of its chromophore to a conserved cysteine residue. A long-term goal of this research is to define the light-regulated signal transduction cascade controlled by RcaE. Despite the progress that has been made in understanding the molecular basis of complementary chromatic adaptation, understanding of the light-regulated mechanism of RcaE activity is incomplete. The detailed aims of this project are as follows: (i) the lyase enzyme(s) responsible for covalent attachment of a chromophore to RcaE will be identified by constructing and screening an appropriate expression library, (ii) a bacterial expression system will be used to isolate chromophorylated RcaE, and (iii) the light-regulated, complex phosphorelay cascade initiated by RcaE will be further characterized. A broader impact of this research is to develop the ability of undergraduate science majors and students from underrepresented groups who are participating in the Undergraduate Researchers in Plant Science Program at Michigan State University to think analytically and critically.