Heterogeneity of three electrophoretically distinct Go alpha-subunits in mammalian brain.

So far three splice variants of the alpha o-gene coding for two alpha o proteins have been identified by molecular cloning, and the corresponding proteins purified. In the present study subtype-specific peptide antibodies revealed the existence of an electrophoretically distinct third form of alpha o in mammalian brain membranes which migrates more slowly on SDS-PAGE and shows a more acidic pI value than the other alpha o-subunits. Each of the three alpha o-subunits is detected as two isoforms when enriched from brain membranes. Rodent alpha o-subunits differ from non-rodent species in their electrophoretic mobilities. The results suggest that (i) there may exist a novel alpha o-subunit which reacts with an alpha o1-subunit-specific antibody, (ii) each alpha o-subunit may exist in more than one co- or posttranslationally modified isoform in brain membranes, and (iii) differences between alpha o-subunits from different species exist which are detectable by gel electrophoretic methods.