A putative Arabidopsis thaliana gene, ara, homologous to the ras-related gene family was isolated from a genomic library by low-stringency hybridization with a v-Ha-ras probe. The putative gene has a coding frame for a 218-residue protein (Mr 24,210), which is interrupted by one intron. The amino acid residues conserved in proteins of the ras gene family, which are important for GTP binding, GTP hydrolysis and membrane attachment, are also present in the ara protein. An unusually long homopyrimidine-homopurine tract was found about 100 bp upstream from the methionine start codon. A unique sequence, 5'-AACAAAACCAAAGTGATATGC-3', was found three times in the 5'-noncoding region and once in the intron.