Figure 1.

Claudin family signature sequence in the predicted 1st extracellular loop. Top: Prosite pattern (accession no. PS01346), which is 89% specific for claudin family members (323). Ambiguities are indicated by listing acceptable amino acids at a given position between square parentheses, “x” is used for a position where any amino acid is accepted, with the range in the number of repetitions indicated in round parentheses. Bottom: updated version to include two other highly conserved residues located upstream and downstream of the classic signature. In addition to standard Prosite syntax, we use uppercase letters to indicate the more frequent residue at a position of ambiguity and lowercase to indicate the rarer one.