Single-channel recordings reveal that the biophysical properties of heterotetrameric and homotetrameric channels differ. Whereas GIRK2 homotetrameric channels have short opening times (<0.5 ms mean open time), the heterotetrameric channels (e.g. GIRK1/GIRK2, GIRK1/GIRK3 or GIRK1/GIRK4) display longer opening times (~1-2 ms mean open times)3,11,23,25,36. The significance of different single channel kinetics is not clear but the direct association of G protein Gβγ subunits with GIRK channels might alter the frequency of long openings, giving rise to large receptor-activated currents37,38.
