Amino acid sequence determination of the novel forms of Goα purified from bovine brain membranes

Abstract
Previously we have reported that there are at least four different forms of Goα in bovine brain membranes which can be distinguished by their elution profiles from Mono Q column and their immunological reactivities. The four α‐subunits are referred to as αo 1, αo 2, αo 3 and αo 4 in their elution orders from the column. Partial amino acid sequences of the purified αo 1 and αo 2 were determined and compared with the predicted sequences of two classes of Goα cDNAs, termed Goα‐1 and Goα‐2. There were at least two unique fragments corresponding with the predicted amino acid sequence of the Goα‐2 cDNA but different from that of the Goα‐1 cDNA upon tryptic digestion of αo 1‐ or αo 2‐subunit. The αo 3‐ and αo 4‐subunits, but not αo 1‐ and αo 2‐subunits, were recognized by an antibody raised against a unique amino acid sequence predicted from Goα‐1 cDNA. These results suggest that αo 1,2 subunits and αo 3,4 subunits are encoded by G.oα‐2 cDNA and Goα‐1 cDNA, respectively.