Abstract
Different molecular species of cytochrome P450 exist in two intracellular organella, the endoplasmic reticulum and mitochondria in eukaryotic cells. Microsomal P450s possess uncleavable signal sequences whose orientation in the membrane is inverted to the signal peptides of secretory proteins. Their unique function is dependent on the balance between the hydrophobic segment and its amino-terminal charges. Mitochondrial P450s possess extension peptides which target the precursor molecules to mitochondria. The precursors are recognized, kept in an import competent state, and targeted to mitochondria by mitochondrial import stimulation factor (MSF).
