Fig. 1. Comparison of the primary structures of amphioxus Bb1C and Bb2C, mouse E-cadherin, and sea urchin LvG-cadherin. The signal sequences and transmembrane segments are indicated by filled black boxes. The arrowhead shown for mouse E-cadherin indicates a proteolytic cleavage site that is utilized in the maturation of this protein (Shirayoshi et al., 1986). The domain organization of each classic cadherin is designated in the parentheses. Domain abbreviations: EC, cadherin extracellular repeat; NC, nonchordate classic cadherin-specific domain; CE, cysteine-rich EGF-like domain; LG, laminin G-like domain; CP, cytoplasmic domain; PCCD complex, primitive classic cadherin domain complex.