Domain organization of mammalian carcinoembryonic antigen (CEA) family members. The domain organization of CEA family members from selected species was predicted by gene analysis and confirmed, where available, by EST (cattle) and cDNA sequences [4, 5, 27, 35]. The conserved members are shown in green, members expressed predominantly in trophoblast cells of the placenta in grey boxes. The predicted signaling motifs in the cytoplasmic domains are schematically shown as green (immunoreceptor tyrosine-based activation motifs; ITAM), blue (ITAM-like motif, no acidic amino acid present at position -1 to -3 from first Y in consensus motif E/Dx0-2YxxL/Ix6-8YxxL/I), red (immunoreceptor tyrosine-based inhibition motifs) and yellow boxes (immunoreceptor tyrosine-based switch motif). Due to gaps in the genomic sequences, some domains could not be clearly identified for a few proteins which are indicated by a question mark. C, CEA-related cell adhesion molecule.