Ontogenetic study of the regulatory and coupling function of guanyl nucleotide-binding proteins in the...

Reconstitution of catecholamine-sensitive adenylate cyclase from chick embryonic muscle membranes and guanyl nucleotide-binding proteins of mature rabbit muscle makes it possible to reveal the coupling (potentiating) effect of these nucleotides 1 week earlier than in the native condition. The effective insertion of guanyl-nucleotide-binding proteins into the embryonic membrane coincides with the onset of a pronounced increase in membrane lipid fluidity during the course of embryogenesis. The different ontogenetic time-courses for the origination of the two guanyl nucleotide effects, on catalytic adenylate cyclase activity (in early embryogenesis) and on the coupling process (in postembryonic life), suggest the existence in this system of two separate guanyl-nucleotide-binding proteins performing regulatory and coupling functions, respectively.