OOCYTE MATURATION IN STARFISH IS MEDIATED BY THE BETA-GAMMA-SUBUNIT COMPLEX OF A G-PROTEIN

The stimulation of meiotic maturation of starfish oocytes by the hormo ne 1-methyladenine is mimicked by injection of betagamma subunits of G -proteins from either retina or brain. Conversely, the hormone respons e is inhibited by injection of the GDP-bound forms of alpha(i1) or alp ha(t) subunits, or by injection of phosducin; all of these proteins sh ould bind free betagamma. alpha-subunit forms with reduced affinity fo r betagamma (alpha(i1) or alpha(t) bound to hydrolysis-resistant GTP a nalogs, or alpha(i1)-GMPPCP treated with trypsin to remove the amino t erminus of the protein) are less effective inhibitors of 1-methyladeni ne action. These results indicate that the betagamma subunit of a G-pr otein mediates 1-methyladenine stimulation of oocyte maturation.