Sequence and gene expression of rabbit cytochrome P450 IIC16: comparison to highly related family members.

Cytochrome P450s are heme containing proteins which evolved from an ancestral gene(s) to form a large superfamily of enzymes. We have isolated a unique cDNA from the rabbit P450 IIC subfamily, IIC16, which is 2028 bp in length. Nucleotide sequence determination indicated an ATG start codon 66 bp from the 5' end of the molecule, and an open reading frame coding for a protein of 487 amino acids. P450 IIC16 protein is greater than or equal to 90% identical in sequence to rabbit P450 IIC4, IIC5, and to the partial sequence available for IIC15. Northern and slot blot experiments demonstrated that the P450 IIC16 gene is expressed constitutively in liver, lung, testes, and kidney, and is inducible by phenobarbital in each tissue with the exception of the kidney, where mRNA levels are repressed. Alignment analysis of eight rabbit P450 IIC proteins revealed conserved and variable regions common to all IIC enzymes, and specific areas are suggested which may be important with respect to structure and function.