Biosynthesis and Assembly of Phycobiliproteins in Cyanobacteria

蓝细菌是世界海洋初级生产力的极其重要的贡献者。为了进行光合作用和固定碳，蓝藻必须吸收光。它们利用被称为藻胆体的捕光复合物实现有效的光吸收，所述复合物含有鲜艳的藻胆蛋白，其吸收光谱的可见光区域中的光。实际的光吸收分子是胆色素发色团，它们通过称为胆色素裂解酶的酶附着在每个藻胆蛋白上。此外，由于存在一种称为藻胆素的黄色发色团，聚球藻属中的一些海洋蓝细菌可以收获主导这些环境的蓝光。本研究的目的是确定黄色藻胆素发色团是如何合成的，以及所有发色团是如何附着到三种聚球藻（PCC 7002，WH8020和WH8102）中的每个藻胆蛋白上的。 在聚球藻WH8020和WH8102的基因组中，通过与其他已知的胆色素裂解酶的序列相似性，已经鉴定了编码这些生物合成过程中潜在酶的几个基因。每个候选基因在发色团附着中的作用将通过重建大肠杆菌细胞内每个藻胆蛋白的生物合成途径来评估。此外，将在体外测定候选重组胆色素裂解酶的藻胆素合成和附着。在与结构生物学家的合作中，将对其中一种胆色素裂解酶进行纯化和结晶，以确定其三维结构。更广泛的影响：除了提供有关光合光收集的基础知识外，这项研究将导致沿着每年培训两到四名本科生和两名研究生。将通过鼓励代表性不足的群体参与科学的机制招募学生。PI将继续与她的高中，本科，MS和博士生合著出版物。PI将她的研究与生物化学和分子生物学实验室课程相结合，每年有20名学生参与。

Cyanobacteria are extremely important contributors to primary productivity in the world's oceans. In order to perform photosynthesis and fix carbon, cyanobacteria must absorb light. They achieve efficient light absorption utilizing light-harvesting complexes called phycobilisomes that contain brilliantly colored phycobiliproteins, which absorb light in the visible region of the light spectrum. The actual light-absorbing molecules are bilin chromophores, which are attached to each phycobiliprotein by enzymes called bilin lyases. Additionally, some marine cyanobacteria in the genus Synechococcus can harvest the blue light that dominates these environments due to the presence of a yellow chromophore called phycourobilin. The goal of this research is to determine how the yellow phycourobilin chromophore is synthesized and how all of the chromophores are attached to each phycobiliprotein in three species of Synechococcus (PCC 7002, WH8020, and WH8102). Several genes that encode potential enzymes in these biosynthetic processes have been identified in the genome of Synechococcus WH8020 and WH8102 by sequence similarity to other known bilin lyases. The role of each candidate gene in chromophore attachment will be evaluated by recreating the biosynthetic pathway for each phycobiliprotein inside Escherichia coli cells. In addition, candidate recombinant bilin lyase enzymes will be assayed for phycourobilin synthesis and attachment in vitro. In collaboration with a structural biologist, one of the bilin lyases will be purified and crystallized in order to determine its three-dimensional structure.Broader impacts: In addition to providing fundamental knowledge about photosynthetic light harvesting, this research will result in training two to four undergraduates per year along with two graduate students. Students will be recruited through mechanisms that encourage participation of underrepresented groups in science. The PI will continue to co-author publications with her high-school, undergraduate, MS, and PhD students. The PI has integrated her research with the curriculum of a Biochemistry and Molecular Biology lab course, reaching 20 students each year.