Is cytochrome P‐450scc a transmembrane protein?

Abstract

The topology of cytochrome P-450_scc in the inner mitochondrial membrane of adrenal cortex has been investigated using monospecific antibodies to cytochrome P-450_scc and its fragments F₁ (Ile¹-Arg²⁵⁰), F₂ (Asn²⁵⁷-Ala⁴⁸¹) and F₃ (Asn²⁵⁷-Arg³⁹⁹). Antibodies to F₁ and F₂ were shown to effectively bind to the matrix and cytosolic sides of the inner membrane. Antibodies to F₃ specifically interacted only with the matrix side of the membrane. These data are consistent with a model of molecular organization which shows that cytochrome P-450_scc is a transmembrane protein, both N- and C-terminal sequences of the cytochrome being able to span the membrane.