MOLECULAR-STRUCTURE OF RAS-RELATED SMALL GTP-BINDING PROTEIN GENES OF RICE PLANTS AND GTPASE ACTIVITIES OF GENE-PRODUCTS IN ESCHERICHIA-COLI

We isolated two rice cDNA clones (ric1 and ric2) encoding proteins homologous to the ras-related small GTP-binding protein. The amino acid sequences of ric1 and ric2 are conserved in four regions involved in GTP binding and hydrolysis which are characteristic in the ras and ras-related small GTP-binding protein genes. In addition, two consecutive cysteine residues near the carboxyl-terminal end required for membrane anchoring are also present in ric1 and ric2. The ric1 and ric2 proteins synthesized in Escherichia coli possessed GTPase activity (i.e. hydrolysis of GTP to GDP).