Fig. 1. Ig-SF proteins at TJs. (A) All Ig-SF proteins present at TJs belong to the CD2 subfamily with a membrane-distal V-type Ig-domain and a membrane-proximal C₂-type Ig-domain. Putative N-linked glycosylation sites are illustrated by dots. Disulfide bridges and putative additional intramolecular disulfide bridges formed by conserved cysteine residues in the C₂-type Ig-domain are indicated. The sizes of the cytoplasmic domains (mouse molecules) are indicated at the bottom of each molecule. TJ localization has so far been shown for JAM-A, JAM-C, CAR, ESAM and JAM4 (see text for details). (B) A phylogenetic tree (Clustal W program, residue weight table PAM250; human CD2 is used as an outgroup) indicates that JAM-A, JAM-B and JAM-C, as well as CAR, ESAM and JAM4, form individual subfamilies. (C) All six Ig-SF molecules end in canonical PDZ domain binding motifs, which are of type II for JAM-A, JAM-B and JAM-C, and type I for CAR, ESAM and JAM4. The subcellular localization of two proteins with a similar structural organization, BT-IgSF (Suzu et al., 2002) and JAML (Moog-Lutz et al., 2003), has not yet been addressed; these molecules are not included in this figure. P, position of the amino acids with respect to the C-terminal aa, which is designated P₀; , hydrophobic residue; X, any residue.