ISOLATION AND SEQUENCE-ANALYSIS OF CYTOCHROME-P450 12B1 - THE FIRST MITOCHONDRIAL INSECT P450 WITH HOMOLOGY TO 1-ALPHA,25 DIHYDROXY-D-3 24-HYDROXYLASE

The biosynthesis of steroid hormones is an integral component of insec t growth, development and reproduction, Although there is an abundance of biochemical data implicating both microsomal and mitochondrial cyt ochrome P450s in steroid metabolism, molecular genetic information on mitochondrial P450s is almost entirely limited to vertebrate sequences , In the current study, a degenerate polymerase chain reaction (PCR) p rimer was targeted to the highly conserved region of P450 genes that e ncodes the heme-binding decapeptide, Using a 5' rapid amplification of cDNA ends (RACE) approach, seven novel cytochrome P450 genes were iso lated from Drosophila acanthoptera, including one sequence (CYP12B1) w ith high regional homology to vertebrate mitochondrial P450s, Sequence analysis of the conceptual translation of the full length gene, obtai ned by 5'RACE, revealed an amphipathic NH2-terminus rich in basic and hydrophilic amino acids, a characteristic feature of mitochondrial P45 0s that distinguishes them from their distantly related microsomal rel atives, Phylogenetically, CYP12B1 appears to be most closely related t o the mammalian mitochondrial P450s of the CYP24 family that play a cr itical role in calcium homeostasis through the metabolism of vitamin D -3, The potential biological role of CYP12B1 is discussed in the light of what is currently known about arthropod calcium binding proteins a nd their regulation, (C) 1997 Elsevier Science Ltd.