MOLECULAR-CLONING OF GUINEA-PIG CYP1A1 - COMPLETE PRIMARY STRUCTURE AND FAST MOBILITY OF EXPRESSED PROTEIN ON ELECTROPHORESIS

Guinea pig CYP1A1 cDNA was isolated from a liver cDNA library of guine a pig treated with 3-methylcholanthrene. The cDNA, named GPc1, was 267 4 bp long and contained an entire coding region for 516 amino acids. T he amino acid sequence of guinea pig CYP1A1 shared 74-78% identity wit h those of the other mammalian CYP1A1s. RNA blot and immunoblot analys es revealed that CYP1A1 was constitutively expressed and was induced b y 3-methylcholanthrene in guinea pig liver. On sodium dodecyl sulfate- polyacrylamide gel electrophoresis, guinea pig CYP1A1 expressed in yea st had a significantly smaller apparent molecular mass than expressed mouse CYP1A1. An alignment of the amino acid sequences of mammalian CY P1A1s demonstrated that guinea pig CYP1A1 was several residues shorter than the counterparts in the N-terminal region. Thus, to clarify the contribution of the N-terminal sequence of guinea pig CYP1A1 to the fa st mobility on the electrophoresis, mouse-guinea pig chimeric CYP1A1 w as prepared through cDNA-directed expression in yeast. The chimeric CY P1A1 protein had an intermediate molecular mass between mouse and guin ea pig CYP1A1s indicating that the anomalous mobility of guinea pig CY P1A1 is in part due to the shortened N-terminal amino acid sequence of the protein.