Evidence for oligomeric forms of transducins alpha subunit: Formation of intermolecular alpha-alpha disulfide linkages

Abstract

Transducin, the retinal G-protein, is a heterotrimeric protein composed of α, β and γ subunits. Intermolecular disulfide linkages between the α-subunits of transducin molecules are spontaneously formed when the purified G-protein is placed in a non-reducing buffer system. The β and γ subunits do not participate in the intermolecular disulfide bridge formation. The α-α subunit disulfide bonds result in the inhibition of transducin activation by bleached rhodopsin which is restored by reducing the disulfides with dithiothreitol. The trapping of oligomers by disulfide bond formation provides physical evidence for specific intermolecular interactions between α-subunits of transducin.