Guanine nucleotide exchange factor (GEF), which can activate some, but not all, G-alpha proteins independently of G-protein coupled receptors. Acts by exchanging bound GDP for free GTP. Able to facilitate synaptic transmission in the nervous system probably by activating G(q)-alpha (egl-30). Also able to activate the G(s)-alpha in synaptic signaling network. Plays a key role in asymmetric spindle positioning, a step for asymmetric cell division that generates cell diversity during development by activating G(i)-alpha protein goa-1 and gpa-16 independently of G-protein coupled receptors. While it acts as a GEF for goa-1, it has no GEF activity toward gpa-16. In addition to its GEF activity, it is required for cortical subcellular localization of G-alpha proteins such as gpa-16. Also required for the interaction of goa-1 and gpr-1/2, suggesting that it may act by generating G-alpha proteins free from G-beta-gamma subunits, enabling gpr-1/2 to mediate asymmetric cell division. Interacts with GDP-bound G-alpha proteins goa-1 and gpa-16. Does not interact with G-alpha proteins when they are in complex with subunits beta and gamma. Localizes to the cell cortex. Excluded from interphase nuclei and becomes localized around what appeared to be kinetochore microtubules at the onset of mitosis, becoming more diffuse during anaphase. Present throughout the nervous system in juveniles and adults (at protein level). Belongs to the synembryn family.