Nucleotide sequence of the Pseudomonas putida cytochrome P-450cam gene and its expression in Escherichia coli.

Cytochrome P-450cam catalyzes the stereospecific methylene hydroxylation of camphor to form 5-exohydroxycamphor and is encoded by the camC gene on the CAM plasmid of Pseudomonas putida, ATCC 17453. The cytochrome P-450cam structural gene has been cloned by mutant complementation in P. putida (Koga, H., Rauchfuss, B., and Gunsalus, I. C. (1985) Biochem. Biophys. Res. Commun. 130, 412-417). We report the complete nucleotide sequence of the camC gene along with 155 base pairs of 5' and 175 base pairs of 3' flanking sequence. Upon comparison of the amino acid sequence derived from the gene sequence to the one obtained from the purified protein (Haniu, M., Armes, L. G., Yasunobu, K. T., Shastry, B. A., and Gunsalus, I. C. (1982) J. Biol. Chem. 257, 12664-12671), five differences were found. The most significant was the addition of a Trp and a Thr residue between Val-54 and Arg-55, thereby increasing the amino acid numbering scheme by 2 after Val-54, bringing the total number of amino acids to 414. Other differences were: Gln-274----Glu-276, Ser-359----His-361, and Asn-405----Asp-407. N-terminal amino acid sequence analysis of the cloned cytochrome P-450cam enzyme expressed in Escherichia coli under the lac promoter showed a faithful translation of the hemo-protein, with the N-terminal Met removed by processing as found in P. putida. Purification to homogeneity of the cloned protein was accomplished by the method used for the CAM plasmid-encoded enzyme of P. putida. The G + C content of the camC gene was found to be 59.0%, caused by a preferred usage of G and C terminated codons. The gene encoding putidaredoxin reductase, camA, was located 22 nucleotides downstream from the cytochrome P-450cam gene. The camA gene initiated with a novel GUG codon, the first such initiator documented in Pseudomonas.