Docking protein which plays a central coordinating role for tyrosine-kinase-based signaling related to cell adhesion. May serve as an activator of SRC and a downstream effector. Interacts with the SH3 domain of FYN and with CRK, SRC, and YES (By similarity). . This is the function of Ensembl gene identifier ENSG00000100842 (EFS, embryonal Fyn-associated substrate).