Purification by Means of Detergents and Properties of Cytochrome b5 from Liver Microsomes

Abstract Cytochrome b5 was solubilized with detergents and purified to an essentially homogeneous state from rabbit liver microsomes. The purified hemoprotein, called b5, had a molecular weight of about 25,000 and existed in solution as an oligomer, which could be depolymerized in 4.5 m urea. Tryptic digestion of detergent b5 yielded a hemoprotein which was identical with cytochrome b5 purified from the tryptic digest of microsomes. It was concluded that cytochrome b5 preparations hitherto purified are protease-resistant cores of the native hemoprotein.