Subunit Composition of Cytochrome

The subunit composition of cytochrome b was analyzed by means of polyacrylamide gel electrophoresis in a dodecylsulfate medium. In contrast to bile acids, the detergent, dodecylsulfate, caused cytochrome b to dissociate into polypeptide(s) and heme. The protein moiety of cytochrome b migrated as one band (Fig. 15). By calibrating the electrophoretic mobility with proteins of known molecular weight, an apparent molecular weight of 30,000 could be attributed to this protein band. 

This molecular weight is equal to half of the molecular weight of cytochrome b estimated in the presence of cholate. Therefore, native cytochrome b may consist of two subunits of about equal size. This conception of the quarternary structure of cytochrome b is further supported 

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