Abstract: Expression systems and methods for the expression of functional membrane polypeptides such as human cytochrome b5 are provided. The systems include recombinant expression vectors capable of expressing soluble fusion proteins that include a solubilizing agent, a linker, and a membrane polypeptide, as well as one or more cleavers, e.g. proteases, capable of cleaving the linker to release the membrane polypeptide. When the fusion protein is expressed, the linker is cleaved by the cleaver to allow association of the membrane polypeptide with a membrane.

Abstract: Expression systems and methods for the expression of functional membrane polypeptides such as human cytochrome b5 are provided. The systems include recombinant expression vectors capable of expressing soluble fusion proteins that include a solubilizing agent, a linker, and a membrane polypeptide, as well as one or more cleavers, e.g. proteases, capable of cleaving the linker to release the membrane polypeptide. When the fusion protein is expressed, the linker is cleaved by the cleaver to allow association of the membrane polypeptide with a membrane.

Abstract: Expression system for components of a desaturase complex is provided. The system includes expression of a desaturase and an oxidoreductase. The system may be used for expression of mycobacterial desaturases or for expression of mammalian desaturases. The system may further include cell-free expression of other components of the desaturase complex. The expression system may include expression of stearoyl-CoA. The expression system may further include expression of cytochrome b5. The expression system may also include expression of cytochrome b5 reductase. The expression system may also include expression of Rv3230c. In addition, methods for assaying the activity of a stearoyl-CoA desaturase in vitro are provided.