Cloning of ho gene from Gracilariopsis lemaneiformis and study on its function on the synthesis of a fluorescent phycoerythrobilin in heterologous hosts

Heme oxygenase catalyzes the rate-limiting step in the degradation of heme to biliverdin. Two new genes of heme oxygenases, ho-1 and ho-2 , were cloned from the red alga Gracilariopsis lemaneiformis . Their corresponding proteins both belonged to Heme 0 superfamily. The full-length DNA of ho-1 contained 696 nucleotides encoding a protein of 231 amino acids, and the full-length DNA of ho-2 contained 819 nucleotides encoding a protein of 272 amino acids. In order to study the functions of HO-1 and HO-2 in synthesis of phycoerythrobilin, plasmids pET-24a(+)- ho1-pebA-pebB and pET-24a(+)- ho2-pebA-pebB were constructed ( pebA , pebB were the coding genes of ferredoxin-dependent bilin reductases (FDBRs) of G. lemaneiformis that were cloned by our laboratory). Then these two plasmids were co-transformed with pACYC-Duet- peBA ( peBA was the coding gene of two subunits of apo-phycoerythrin), respectively, into E.coli BL21 (DE3). The recombinant proteins presented the characteristic peak of phycoerythrin at 580 nm by fluorescence spectroscopy detection, and the maximum peak appeared at 15 h. The study of heme oxygenase had a positive effect on studying of the pathway for the synthesis of a fluorescent phycoerythrobilin in Gracilariopsis lemaneiformis .