GTP-binding protein Di-Ras1 (DIRAS1) also known as Ras-related inhibitor of cell growth (RIG) is a protein that in humans is encoded by the DIRAS1 gene and is located on the chromosome band 10p13.3. This gene is a member of the Ras superfamily and is highly expressed in heart and brain tissue. DIRAS1 varies from other members of the Ras superfamily due to amino acid substitution in the RAF kinase and Ha-RAS, critical for GTP hydrolysis. Due to these substitution, DIRAS1 has a low level of GTPase activity and exists as the GTP-bound form leading to the hypothesis that DIRAS1 may regulate cell development in a different manner than other members of the Ras superfamily.
DIRAS1 is linked to human glioblastoma, colorectal cancer, renal cell carcinoma, and ovarian cancer. The DIRAS1 gene includes two exons with a 597 bp protein-coding region. The DIRAS1 protein is a GTPase belonging to the Ras superfamily and shares 40–50% homology with Ras and Rap. DIRAS1 differs from the more well-researched DIRAS3 in the length of its N-terminal extensions.
