Identification of G alpha 11 as the phospholipase C-activating G-protein of turkey erythrocytes

Abstract

A 43 kDa phospholipase C-activating protein has been purified previously from turkey erythrocytes and shown to express immunological properties expected of that of the Gq family of G-protein alpha-subunits [Waldo, Boyer, Morris and Harden (1991) J. Biol. Chem. 266, 14217-14225]. Internal amino acid sequence has now been obtained from this protein which shares 50-100% sequence identity with sequences encoded by mammalian G alpha 11 and G alpha q cDNAs. To identify the purified protein unambiguously, it was necessary to compare its amino acid sequence with the sequence encoded by avian G-protein alpha-subunit cDNA. As such, mouse G alpha q was used as a probe to screen turkey brain and fetal-turkey blood cDNA libraries. A full-length cDNA was identified that encodes avian G alpha 11, on the basis of its 96-98% amino acid identity with mammalian G alpha 11. All eight peptides sequenced from the turkey erythrocyte phospholipase C-activating protein are completely contained within the deduced amino acid sequence of the avian G alpha 11 cDNA. Expression of this cDNA in Sf9 cells by using a baculovirus expression system resulted in the production of a 43 kDa protein that reacts strongly with antisera to the Gq family of G-protein alpha-subunits and activated purified avian phospholipase C in an AlF4(-)-dependent manner. Taken together, these results unambiguously identify the protein purified from turkey erythrocytes, on the basis of its capacity to activate avian phospholipase C, as G alpha 11.