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

蓝藻和其他光合生物具有对波动的光照做出精细调整的能力。蓝藻在其光合作用的光收集天线复合体中含有吸收光的藻胆蛋白，称为藻胆异构体。一些蓝藻具有改变其藻胆异构体中藻胆蛋白的组成和浓度以响应光环境变化的能力。这种能力被称为互补色适应，它本身是由一种光感胆蛋白RcaE控制的。来自蓝细菌freremyella diplosiphon的RcaE对绿光和红光都有反应。最近的研究表明，在体内，RcaE需要一个酶促蛋白伴侣来将其发色团与保守的半胱氨酸残基共价连接。本研究的长期目标是明确由RcaE控制的光调节信号转导级联。尽管在了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了解尚不完整。该项目的详细目标如下：(i)通过构建和筛选合适的表达文库来鉴定负责发色团与RcaE共价连接的裂解酶(s), （ii）细菌表达系统将用于分离染色质磷酸化的RcaE，以及（iii）由RcaE启动的光调控的复杂磷接力级联将进一步表征。这项研究的一个更广泛的影响是培养本科理科专业的学生和参加密歇根州立大学植物科学本科研究人员项目的代表性不足的群体的学生的分析性和批判性思维的能力。

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.