CAREER: Elucidation of the Biosynthetic and Degradative Pathways for Phycobiliproteins in Cyanobacteria

光合生物必须平衡它们的新陈代谢和生长条件。蓝藻细菌合成并降解它们的光收集蛋白，称为藻胆蛋白，以响应环境参数，如光强度、光质量和营养物质的可用性。藻胆蛋白吸收可见光区域的光由于它们的十亿蛋白发色团。该研究项目的长期目标是了解蓝藻如何合成和降解藻胆蛋白及其十亿蛋白发色团。第一个目标是表征参与将胆磷脂附着到藻胆蛋白上的酶。Synechocystis sp. PCC 6803中被认为参与十亿蛋白附着的五种蛋白的作用将通过诱变、体外酶测定和大肠杆菌体内异种测定来表征。第二个目标是验证一种新型甲基转移酶的活性，该酶负责将甲基添加到藻胆蛋白β亚基中的保守天冬酰胺残基上。缺乏这种酶的突变体将被表征以评估这种修饰的生理意义。第三个目标是创建和表征突变菌株，其中十亿蛋白生物合成基因pcyA已被中断。将对该突变株中其他四吡咯的合成和调控进行表征。该职业发展计划还包括对本科生和研究生进行研究的培训，并包含鼓励初中生、高中生和本科生考虑科学职业的创新努力。此外，还将开设新的课程，培养生物学学生掌握现代分子和生化技术。本项目由分子生物化学和代谢生物化学项目联合资助。

Photosynthetic organisms must balance their metabolism with the growth conditions. Cyanobacteria synthesize and degrade their light harvesting proteins, called phycobiliproteins, in response to environmental parameters such as light intensity, light quality, and nutrient availability. The phycobiliproteins absorb light in the visible region due to their bilin chromophores. The long-term goal of this research project is to understand how cyanobacteria synthesize and degrade phycobiliproteins and their bilin chromophores. The first objective is to characterize enzymes that are involved in attaching the bilins to phycobiliproteins. The role of five proteins within Synechocystis sp. PCC 6803 that are believed to be involved in bilin attachment will be characterized by mutagenesis, by in vitro enzyme assays, and by heterologous in vivo assays in Escherichia coli. A second objective is to verify the activity of a novel methyl transferase that is responsible for adding a methyl group to a conserved asparagine residue within phycobiliprotein beta-subunits has been identified. A mutant lacking this enzyme will be characterized to assess the physiological significance of this modification. A third goal involves the creation and characterization of mutant strain in which the bilin biosynthetic gene pcyA has been interrupted. Characterization of the synthesis and regulation of other tetrapyrroles within this mutant strain will be performed. This career development plan also includes training of the undergraduate and graduate students in performing the research and contains innovative efforts for encouraging junior high, high school, and undergraduate students to contemplate scientific careers. Additionally, new coursework will be created to train biology students in modern molecular and biochemical techniques. This project is funded jointly by the Molecular Biochemistry and Metabolic Biochemistry Programs.