lymphocyte antigen 6 complex locus protein G6f is a single-pass type I membrane protein belonging to the immunoglobulin (Ig) superfamily. Located in the class III region of the major histocompatibility complex (MHC), the G6f gene lies in a cluster of genes encoding cell-surface proteins that play a role in the immune system and cellular recognition. G6f functions as a downstream effector of GRB2 and GRB7, and, in humans, it interacts with GRB2 and GRB7 through the phosphorylation of a tyrosine residue (Tyr 281) in the intracellular tail of G6f. This interaction is also mediated by the SH2 domain of GRB2 and possibly that of GRB7. G6f is a 297 amino acid protein, and it forms a disulfide-linked homodimer.