Expression of the blue copper protein azurin from Pseudomonas aeruginosa in Escherichia coli

The structural gene for the blue copper protein azurin from Pseudomonas aeruginosa has been subcloned in different expression plasmid vectors. The highest yield of expression was obtained when the gene with its native ribosome-binding site was placed downstream of the lac promoter in plasmid pUC18. The protein is exported to the periplasmic space in Escherichia coli and the amount corresponds to 27% of the total protein content in the periplasmic space. The preprotein is cleaved correctly according to N-terminal sequencing of the purified protein. Azurin has been purified in large amounts and is spectroscopically indistinguishable from the protein purified from P. aeruginosa.