Functions as a guanine nucleotide exchange factor (GEF) activating either RalA or RalB GTPases and plays an important role in intracellular transport. Interacts and acts as an effector molecule for R-Ras, H-Ras, K-Ras, and Rap (PubMed:27773821). During bacterial clearance, recognizes 'Lys-33'-linked polyubiquitinated TRAF3 and subsequently mediates assembly of the exocyst complex (By similarity). Interacts with RIT1 and RIT2 (By similarity). Interacts with OOG1 (PubMed:16580637). Interacts with TRAF3 (By similarity). Interacts with HRAS (PubMed:27773821). Localizes mainly in the peripheral region of the cytoplasmic membrane in oocytes and in preimplantation embryos until the 8-cell stage. Between the late 1-cell and the early 2-cell stages, nuclear localization becomes stronger. After the 4-cell stage, not detected in the nucleus. Expressed in the ovarian oocytes from the primary follicle stage to the antral follicle stage (at protein level). Expressed in preimplantation embryos until the early 2-cell stage, decreasing thereafter. The Ras-associating domain interacts with Ras. Phosphorylation of Tyr-752 by MET blocks HRAS binding.