The human G6f protein(C6orf21) is a type I transmembrane protein belonging to the immunoglobin (Ig) superfamily, which is comprised of cell-surface proteins involved in the immune system and cellular recognition.It may also play a role in the downstream signal transduction pathways involving GRB2 and GRB7.The human G6f protein is a type I transmembrane protein belonging to the immunoglobin (Ig) superfamily, which is comprised of cell-surface proteins involved in the immune system and cellular recognition (de Vet et al., 2003 [PubMed 12852788]).[supplied by OMIM].