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

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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.