IDENTIFICATION OF SOME OF THE BRAIN GN27 AS THE RAL GENE-PRODUCT - COMPARISON BETWEEN THE BRAIN AND PLATELET GN-PROTEINS

Two major G(n)-proteins, G(n)27 and G(n)26, were detected in the 100,000 x g(av) particulate fraction of rabbit and bovine brain. The G(n)26 protein was also present in significant amounts (approximately 50% of total) in the brain supernatant fraction. An antiserum raised against recombinant simian ralA recognized a 27-kDa brain protein with the same apparent molecular mass as the G(n)27 protein. In further analysis by two-dimensional polyacrylamide gel electrophoresis, the brain particulate G(n)-proteins were resolved into 6 major forms, four of 27 kDa (G(n)27 a-d) and two of 26 kDa (G(n)26a and G(n)26b). Minor GTP-binding components were also observed at 25 kDa. The ralA antibody reacted strongly with the brain G(n)27b form and weakly with the G(n)27a and G(n)27c but not with G(n)27d or any of the other G(n)-proteins. In addition, comparison of human platelet and bovine brain particulate G(n)-proteins by two-dimensional polyacrylamide gel electrophoresis demonstrated a tissue/cell-type specific expression of the various forms of G(n)-proteins.