CLONING AND CORRECT EXPRESSION IN ESCHERICHIA-COLI OF THE PETJ GENE ENCODING CYTOCHROME-C(6) FROM SYNECHOCYSTIS-6803

Cytochrome c(6) from the cyanobacterium Synechocystis 6803 has been isolated and purified to electrophoretic homogeneity. The gene coding for such a heme protein (petJ) has been cloned and properly expressed in E. coli. This procedure yields a protein preparation completely identical to that obtained from the cyanobacterial cells. The N-terminal amino acid sequences of cytochrome c, synthesized in both organisms are the same, thus allowing us to conclude that the petJ gene product is correctly processed in E. coli. To the best of our knowledge, this is the first time that any cytochrome c, is produced in the enterobacterium. The identical physicochemical and kinetic properties of the proteins isolated from both sources confirm that expression of the petJ gene in E. coli is an adequate tool to address the study of Synechocystis cytochrome c(6) by site-directed mutagenesis in a parallel way to that carried out with plastocyanin from the same organism.