Date of Award


Degree Type


Degree Name


Degree Program

Biological Sciences


Biological Sciences

Major Professor

Schluchter, Wendy

Second Advisor

Timpte, Candace

Third Advisor

Clancy, Mary


The goal of this research is to identify and characterize enzymes responsible for posttranslational modifications of phycobiliproteins (PBP) in the cyanobacterium Synechocystis sp. PCC 6803. Asparagine 72 is methylated to produce gamma-N-methylasparagine on beta subunits of PBP in vivo. A candidate for this methyl transferase is CpcM (sll0487). Methylase assays showed that CpcM is specific for the beta subunits of PBP with no methylation on the homologous alpha subunits. CpcM methylates PBP after chromophorylation but before the PBP assemble into trimers. Candidates for the lyases responsible for attachment of phycocyanobilin to phycocyanin in Synechocystis sp. PCC 6803 are two cpeS-like genes (cpcS and cpcU) and one cpeT-like gene (cpcT). Through absorbance and fluorescence spectra, it was determined that CpcS and CpcU together catalyze the addition of phycocyanobilin to Cys-82 on betaphycocyanin in vitro and that CpcT is a lyase that adds phycocyanobilin to Cys-153 on betaphycocyanin.


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