Ras-GTPase Activating Domain of proteins similar to neurofibromin
Neurofibromin-like proteins include the Saccharomyces cerevisiae RasGAP proteins Ira1 and Ira2, the closest homolog of neurofibromin, which is responsible for the human autosomal dominant disease neurofibromatosis type I (NF1). The RasGAP Ira1/2 proteins are negative regulators of the Ras-cAMP signaling pathway and conserved from yeast to human. In yeast Ras proteins are activated by GEFs, and inhibited by two GAPs, Ira1 and Ira2. Ras proteins activate the cAMP/protein kinase A (PKA) pathway, which controls metabolism, stress resistance, growth, and meiosis. Recent studies showed that the kelch proteins Gpb1 and Gpb2 inhibit Ras activity via association with Ira1 and Ira2. Gpb1/2 bind to a conserved C-terminal domain of Ira1/2, and loss of Gpb1/2 results in a destabilization of Ira1 and Ira2, leading to elevated levels of Ras2-GTP and uninhibited cAMP-PKA signaling. Since the Gpb1/2 binding domain on Ira1/2 is conserved in the human neurofibromin protein, the studies suggest that an analogous signaling mechanism may contribute to the neoplastic development of NF1.
Jiyao W et al.(2023). "The conserved domain database in 2023.",