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

蓝藻和其他光合作用生物具有微调对光照波动的反应的能力。蓝藻在其光合作用的捕光天线复合体中含有吸收光的藻胆蛋白，称为藻胆体。一些蓝藻具有改变其藻胆体中所含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染色适应，它本身由一种感光胆蛋白RcaE控制。蓝藻Fremyella diplosiphon的RcaE对绿光和红光都有响应。最近的研究表明，在体内，RcaE需要一个酶蛋白伙伴来将其发色团共价连接到保守的半胱氨酸残基上。这项研究的一个长期目标是确定RcaE控制的光调控信号转导级联。尽管在理解互补颜色适应的分子基础方面已经取得了进展，但对RcaE活性的光调控机制的理解还不完整。该项目的具体目标如下：(I)通过构建和筛选合适的表达文库，鉴定负责生色团与RcaE共价结合的裂解酶(S)；(Ii)利用细菌表达系统分离发色素化的RcaE；(Iii)进一步鉴定RcaE启动的光调控的复杂的磷光传递级联。这项研究的一个更广泛的影响是培养本科生和参加密歇根州立大学植物科学本科生研究计划的学生的分析和批判性思考的能力。

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.