Solubilization of a vectorial transmembrane receptor in functional form: aspartate receptor of chemotaxis

The aspartate receptor, an integral membrane protein in the bacterial chemosensory system, has been solubilized in functional form by a combination of detergent, phospholipid, and glycerol. The conformation of the solubilized receptor is the same as that of the protein in vivo, as indicated by aspartate binding, rates of methyl esterification, and quantitative correlation of stimulus with this covalent modification. Studying the functional solubilized receptor in a homogeneous solution avoids many difficulties associated with an in vivo or a vesicle-reconstituted receptor. The technique of adding lipids, detergent, and glycerol to solubilize the protein in active form appears to be generally applicable.