IRTA family proteins have related extracellular and cytoplasmic domains, which can be grouped into domain subtypes.

Conservation and relatedness to Fc receptor family members. Ovals represent extracellular Ig superfamily domains, with IRTA domain subtype indicated by letters “A” through “E.” The extent of conservation of each domain is represented by its degree of shading, as shown in the key. Patterned rectangles represent transmembrane regions. Straight lines (not to scale) represent cytoplasmic domains. ITIM indicates immunotyrosine inhibitory motif; ITIM,immunotyrosine inhibitory motif–like sequence. Potential ITAM pairs are bracketed.