Ca2+-dependent cell -cell adhesion molecules, termed cadherins, are divided into subclasses with distinct tissue distributions and distinct cell-binding specificities. To elucidate the biochemical relationship of these subclasses, we compared the pattern of tryptic cleavage and the partial amino acid sequence of mouse liver E-cadherin with those of chicken brain N-cadherin. Although these two cadherins are distinct in their cell-binding and immunological specificities, they showed an identical mol. wt and a similar tryptic cleavage pattern. We isolated tryptic fragments of E-and N-cadherin, and determined the sequences of nine amino acid residues of their amino terminus. The results showed that sequences of amino acids from the amino terminus to the 7th residues are identical in these two cadherins. We thus suggest that cadherins with distinct specificities have a common genic origin. Key words: adhesive specificity/amino acid sequence/cadherins/ cell -cell adhesion in in vitro experiments (Takeichi et al., 1985b). We also observed that cells expressing N-cadherin segregate from cells expressing E-cadherin during normal morphogenetic processes such as gastrulation and neural tube formation (Hatta and Takeichi, 1986). These observations prompted us to elucidate the biochemical basis of the binding specificity of heterotypic cadherins. In the present study, we isolated E-cadherin from mouse liver and N-cadherin from chicken brain, compared their patterns of trypsin sensitivity and determined their amino-terminal amino acid sequences. The results show that these two cadherins display a common tryptic cleavage pattern and possess an identical amino acid sequence extending from the amino terminus to the seventh amino acid residue. We thus suggest that cadherin subclasses with distinct specificities have a common genic background, constituting a 'cadherin family'.

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