CLONING OF 5 HUMAN CADHERINS CLARIFIES CHARACTERISTIC FEATURES OF CADHERIN EXTRACELLULAR DOMAIN AND PROVIDES FURTHER EVIDENCE FOR 2 STRUCTURALLY DIFFERENT TYPES OF CADHERIN

The entire coding sequences for five possible human cadherins, named c adherin-4, -8, -11, -12 and -13, were determined. The deduced amino ac id sequences of cadherin-4 and cadherin-13 showed high homology with t hose of chicken R-cadherin or chicken T-cadherin, suggesting that cadh erin-4 and cadherin-13 are mammalian homologues of the chicken R-cadhe rin or T-cadherin. Comparison of the extracellular domain of these pro teins with those of other cadherins and cadherin-related proteins clar ifies characteristic structural features of this domain. The domain is subdivided into five subdomains, each of which contains a cadherin-sp ecific motif characterized by well-conserved amino acid residues and s hort amino acid sequences. Moreover, each subdomain has unique feature s of its own. The comparison also provides additional evidence for two structurally different types of cadherins: the first type includes B- , E-, EP-, M, N-, P- and R-cadherins and cadherin-4; the second type i ncludes cadherin-5 through cadherin-12. Cadherin-13 lacks the sequence corresponding to the cytoplasmic domain of typical cadherins, but the extracellular domain shares most of the features common to the extrac ellular domain of cadherins, especially those of the first type of cad herins, suggesting that cadherin-13 is a special type of cadherin. The se results, and those of other recent cloning studies, indicate that m any cadherins with different properties are expressed in various tissu es of different organisms.