l The functioning of heterotrimeric G protein a subunits in the transduction of hormonal signals to appropriate intracellular responses is well recognized. Much less is known about the distribution of isoforms and functions of G protein p subunits. Here, using specific antibodies, we documented that in plasma membranes of the thyroid cell line Nthy-ori 3-1 all G beta isoforms-G beta(1), G beta(2), G beta(3), G beta(4) and G beta(5) are present, while the G beta(3) occurs in minute amount. In plasma membrane fraction isolated from pooled postoperative thyroids of patients with nodular goiter and Graves' disease, the G beta(1), G beta(2), G beta(3) and G beta(5) subunits were found, whereas G beta(3) could not be detected. Competition studies revealed that the G beta(2) is the principal G beta subunit in membranes from cultured thyroid cells, originated from normal thyroid, as well as in membranes from patients' thyroids. This suggests that G beta(2) subunit cooperates with Gas subunit, the most active of the Got variants, during stimulation of adenylate cyclase which constitutes the main route of physiological thyroid stimulation. (C) 2011 Elsevier Inc. All rights reserved.