Immunochemical comparison of pertussis toxin substrates in brain and peripheral tissues

The tissue distribution of pertussis toxin-sensitive GTP-binding proteins was examined using specific antibodies raised against the purified alpha-subunit of G0 from bovine brain or against synthetic peptides predicted from cDNAs for distinct Gi subtypes. GTP-binding proteins were partially purified from membrane fractions prepared from rabbit tissues including brain, heart, liver, lung, erythrocytes and neutrophils. Brain contained both G0 and Gi1. Gi1 was also found to be abundant in heart. All peripheral tissues contained readily detectable amounts of Gi2, whereas only barely detectable amounts of Gi2 were found in brain. Gi3 was found to be prominent in erythrocytes and exists as a minor component of G proteins in neutrophils and liver. Thus, Gi2 appears to be widely disseminated in peripheral rabbit tissues, while other pertussis toxin substrates are more limited in their distribution.