Extraction of a steroid transport system from Pseudomonas testosteroni membranes and incorporation into synthetic liposomes.

A steroid binding protein has been extracted from Pseudomonas testosteroni membranes with an organic solvent system. This protection binds some C19 and C21 steroids but not C18 steroids. When this protein is incorporated into synthetic lipid vesicles constructed from P. testosteroni phospholipids, the vesicles perform concentrative uptake of testosterone in the presence of the ionophore valinomycin. This steroid binding protein is thus believed to be the steroid permease of this organism.