Molecular characterization of a novel gene from Synechocystis sp. PCC 6803

A novel gene slr2049 was identified in Synechococcus sp. PCC7002 by homologous alignment. The features and possible functions of slr2049 gene were predicted by bioinformatics analysis. The function of slr2049 was analyzed in vitro with a heterologous Escherichia coli system with plasmids conferring biosynthesis of phycocyanobilin (PCB) and of the acceptor proteins, β-phycocyanin (CpcB). The resulting products were evaluated with SDS-PAGE and absorption spectra. The function of slr2049 was further analyzed via site-directed mutations. Two mutants, slr2049 (W14L) and slr2049 (Y132S) were generated. The results showed that Slr2049 could catalyze the chromophorylation of CpcB. Compared to wild type, mutant Slr2049 (W14L) had red-shifted absorbance maxima and was not highly fluorescent as the wild-type. However, mutant Slr2049 (Y132S) was almost the same as the wild-type. In conclusion, our study suggests that we have cloned a novel gene and this gene may play an important role in attachment of the chromophores to the apo-proteins.