Cloning, expression and characterization of phycoerythrin gene from Ceramium boydenn

Phycobiliproteins function as a major light harvesting protein-pigment complex in the cyanobacteria and the eukaryotic algae. Phycoerythrin (PE) is a kind of phycobiliproteins, widely located in all rhodophytes, some species of cyanobacteria and cryptophytes, and different ecotypes of Prochlorococcus populations. PeBA encoding beta and alpha subunits of PE from Ceramium boydenn was cloned and sequenced in this research. A peBA specific PCR primer was synthesized, based on the peBA gene conserved sequences. The beta subunit encoding gene (peB) contained an open reading frame of 534 bp, while the alpha subunit (peA) was 495 bp. Recombinant expression plasmid pET-peAB was constructed and expressed in Escherichia coli BL21. The molecular weight of expressive product of peB and peA was about 23.3 and 18.2 KD, respectively. Results of codon usage analysis show that G + C content is heterogeneous among different groups of PE and spacers have dramatically lower G + C contents than coding regions. Also there is a high variance in G + C content among sequences at the third position sites. It is also found in this paper that several sequence regions, which might reflect functional or structural requirements of the PE organization, and several residues known for their functional importance are conserved in almost all the sequences.