SPECIFICITY OF THE CYTOCHROME-P-450 INTERACTION WITH CYTOCHROME B(5)

The specificity of the interaction of cytochrome b(5) with different f orms of cytochrome P-450 was examined. Immunopurification of cytochrom es P-450 1A1, 2B1 and 2E1 from rat liver microsomes resulted in co-pur ification of cytochrome b(5) with cytochrome P-450 forms 2B1 and 2E1 b ut not 1A1. This specificity was evaluated in conjunction with multipl e sequence alignment of the three cytochrome P-450s and a molecular mo del of the cytochrome P-450-cytochrome b(5) complex [(1989) Biochemist ry 28, 8201-8205]. These analyses suggest two basic residues in the ar ginine cluster region of P-450, which are present in P-450s 2B1 and 2E 1 but are absent in P-450 1A1, as potential binding sites for cytochro me b(5).