[Secretory expression of salmon calcitonin in Streptomyces lividans]

A gene coding for salmon calcitonin precursor (sCT-Gly) was amplified from salmon genomic DNA by Polymerase Chain Reaction (PCR) and fused to the expression and secretion signals of melC1 amplified by PCR. The fusion gene was cloned into the Streptomyces vector pIJ680 and expressed under the control of aminoglycoside phosphotransferase gene (aph) promoter. Streptomyces lividans TK54 transformed with the expression plasmid (pMS680) secreted biologically active sCT-Gly into the culture medium which was confirmed by Enzyme Immunoassay (EIA) and bioassay. Production of sCT-Gly by the recombinant strain in YEME medium reached a maximum of 100 micrograms/L culture at about 96 h. The recombinant sCT-Gly had almost the same HPLC retention time as the standard sCT obtained from Sigma.