Camphor hydroxylase of Pseudomonas putida: vestiges of sequence homology in cytochrome P-450CAM, putidaredoxin, and related proteins.

The amino acid sequences of cytochrome P-450CAM and putidaredoxin of the camphor hydroxylase [camphor, reduced-putida-ferredoxin:oxygen oxidoreductase (5-hydroxylating), EC 1.14.15.1] of Pseudomonas putida are compared to each other and then to the sequences of bovine adrenodoxin and cytochrome b5. The comparisons reveal areas of homology indicating that these four proteins may share a common evolutionary origin. Moreover, homologous segments can be recognized by proper alignment of the sequence of cytochrome P-450CAM to recently determined sequences of other P-450 hemeproteins. Further scrutiny indicates vestiges of internal sequence duplications that have been conserved in limited segments by the constraints of selection over a long time period, while other segments of the sequence diverged. It is predicted that the corresponding reductases will show a similar sequence pattern. The conserved regions of internal sequence repetition may serve a special purpose in protein-protein interactions within the multienzyme systems.