A monoclonal antibody that causes the heterotrimeric G-protein G(o) to release its beta gamma subunits

Heterotrimeric (alpha beta gamma) guanine nucleotide binding proteins (G-proteins) dissociate into their constituent subunits in the course of signal transduction. Exposure of the G-protein G(o) to the alpha(o)-specific monoclonal antibody 3E7 results in recovery of alpha(o) alone. We identified the 3E7 epitope as ERSKAIEKNL (positions 14-23) using synthetic peptides and phage display. G(o) isolated with alpha(o)-specific monoclonal antibodies MONO and 3C2 dissociates and releases its beta gamma subunits when exposed to 3E7. Exposure to 3E7, but not MONO or 3C2, results in the displacement of beta gamma from trimers, in the absence of added activators of G-proteins (GTPgammaS, Mg2+AlF4-). We propose that stable binding of 3E7 to alpha(o) requires displacement of beta-gamma and occurs in the absence of guanine nucleotide exchange.