Guanine nucleotide exchange factor (GEF) for Rho and Rac (PubMed:38857861). GEF proteins activate small GTPases by exchanging bound GDP for free GTP (By similarity). Together with ELMO1, activates RAC1; the activity is stimulated by RHOG (PubMed:38857861). Along with DOCK1, mediates CRK/CRKL regulation of epithelial and endothelial cell spreading and migration on type IV collagen (PubMed:19004829). {ECO:0000250|UniProtKB:B2RY04, ECO:0000269|PubMed:19004829, ECO:0000269|PubMed:38857861}. This is the function of DOCK5 (dedicator of cytokinesis 5, ENSG00000147459).