C-terminal SARAH domain found in Ras-association domain proteins, RASSF1, RASSF3, and RASSF5
The RASSF subfamily of proteins shares a conserved RalGDS/AF6 Ras association (RA) domain which is located either at the C-terminus (RASSF1-6, the classical group) or at the N-terminus (RASSF7-10). Classical RASSF proteins interact either directly or indirectly with activated Ras. Ras proteins are small GTPases that are involved in cellular signal transduction. They seem to modulate some of the growth inhibitory responses mediated by Ras and may serve as tumor suppressor genes. RASSF1-6 contains a conserved SARAH (Salvador-RassF-Hippo) motif adjacent to the RA domain that functions in scaffolding and regulatory interactions. The RA domain of the classical RASSF proteins has a beta-grasp ubiquitin-like fold with low sequence similarity to ubiquitin. This model corresponds to the SARAH domain of RASSF1, RASSF3, and RASSF5. It is a characteristic coiled-coil structure that is important in signal-transduction networks. The central function of the SARAH domain is the mediation of homo- and heterodimerization between SARAH domain-containing proteins.