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 the enzymes (lyases) responsible for chromophore (bilin) attachment to phycobiliproteins (light harvesting) in cyanobacteria. Candidates for these lyases were first identified in Fremyella diplosiphon as cpeS and cpeT. In Synechococcus sp. PCC 7002, there are three cpeS-like genes (named cpcS, cpcU, and cpcV) and one cpeT-like gene (named cpcT). These genes were cloned, overexpressed, and purified from E. coli. The CpcS and CpcU proteins form a 1:1 complex and catalyze the addition of phycocyanobilin (PCB) to â-82 cysteinyl residue on phycocyanin (PC) in vitro. Tryptic digestion and C18 RP-HPLC confirmed that CpcSU attached bilin at â-82 cysteine. CpcT was also shown to be a lyase specific for â-153 cysteine as confirmed by tryptic digestion and C18 RP-HPLC. CpcSU together and CpcT alone act as phycobiliprotein lyases that added PCB to â- 82 and â-153 cysteinyl residues of phycocyanin respectively, making these proteins a new family of phycobiliprotein lyases.


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