The ram: A novel low molecular weight GTP‐binding protein cDNA from a rat megakaryocyte library

Abstract
A novel low Mr GTP‐binding protein cDNA was isolated from a rat megakaryocyte cDNA library with a synthetic oligonucleotide probe corresponding to an 8‐amino acid sequence specific for c25KG, a GTP‐binding protein previously isolated from human platelet cytosol fraction [(1989) J. Biol. Chem. 264, 17000–17005]. The cDNA has an open reading frame encoding a protein of 221 amino acids with a calculated Mr of 25068. The protein is designated as ram (ras‐related gene from megakaryocyte) protein (ram p25). The amino acid sequence deduced from the ram cDNA contains the consensus sequences for GTP‐binding and GTPase domains. ram p25 shares about 23%, 39% and 80% amino acid homology with the H‐ras, smg25A and c25KG proteins, respectively. The 3.5‐kb ram mRNA was detected abundantly in spleen cells.