cis/trans isomerase of unsaturated fatty acids of Pseudomonas putida P8: Evidence for a heme protein of the cytochrome c type

From a pool of 600 temperature-sensitive transposon mutants of Pseudomonas putida P8, 1 strain was isolated that carries a mini-Tn5 insertion within t he cytochrome c operon. As a result,: genes involved in the attachment of h eme to cytochrome c-type proteins are turned, off. Accordingly, cytochrome c could not be detected spectrophotometrically. The mutant also exhibited a remarkable reduction of cis-trans isomerization capability for unsaturated fatty acids. Consistent with the genetic and physiological data is the det ection of a cytochrome c-type heme-binding motif close to the N terminus of the predicted polypeptide of the cis/trans isomerase (cti) gene (CVACH; co nserved amino acids in italics). The functional significance of this motif was proven by site-directed mutagenesis. A possible mechanism of heme-catal yzed eis-trans isomerization of unsaturated fatty acids is discussed.