This entry represents the SH2 domain of EAT-2 (EWS-Fli1-activated transcript-2) and ERT (EAT-2-related transducer).The X-linked lymphoproliferative syndrome (XLP) gene encodes SAP (also called SH2D1A/DSHP) a protein that consists of a 5 residue N terminus, a single SH2 domain, and a short 25 residue C-terminal tail []. XLP is characterized by an extreme sensitivity to Epstein-Barr virus. Both T and natural killer (NK) cell dysfunctions have been seen in XLP patients. SAP binds the cytoplasmic tail of Signaling lymphocytic activation molecule (SLAM), 2B4, Ly-9, and CD84 []. SAP is believed to function as a signaling inhibitor, by blocking or regulating binding of other signaling proteins. SAP and the SAP-like protein EAT-2 recognize the sequence motif TIpYXX[VI], which is found in the cytoplasmic domains of a restricted number of T, B, and NK cell surface receptors and are proposed to be natural inhibitors or regulators of the physiological role of a small family of receptors on the surface of these cells [, ]. EAT-2 (also known as SH2 domain-containing protein 1B or SH2D1B) and ERT (also known as SH2 domain-containing protein 1C or SH2D1C), similar to SAP, are composed of a single SH2 domain and a short C terminus. They share approximately 50% amino acid identity with SAP [].
