Pertussis toxin-sensitive G protein participating in starfish oocyte maturation induced by 1-methyladenine

Abstract

Summary 1-Methyladenine (1-MA) secreted from the follicle cells is the biological signal for meiosis reinitiation of starfish oocytes. The signal of-1-MA is transduced into cytoplasmic formation of maturation-promoting factor (MPF) that eventually induces a germinal vesicle breakdown (GVBD). Microinjection of pertussis toxin (PTX) inhibited 1-MA-induced GVBD in Asterina pectinifera and Asterina (Patina) miniata. PTX-inhibition of GVBD was rescued by the injection of MPF into PTX-preinjected oocytes. Most of the PTX- and MPF-double injected eggs were fertilized and underwent cleavage, suggesting the presence of a GTP-binding protein (G protein) specific for 1-MA signal transduction. Indeed, plasma membrane preparations of A. pectinifera oocytes contained a G protein consisting of 39-kDa α, 37-kDa β, and 8-kDa γ subunits. The α subunit contained a site for ADP-ribosylation catalyzed by PTX. It was also recognized by antibodies specific for a common GTP-binding site of mammalian α subunits or a carboxy-termi...