Amino acid sequence of a C-type lectin CEL-IV from the marine invertebrate Cucumaria echinata

The complete amino acid sequence of a Ca(2+)-dependent lectin, CEL-IV, from the marine invertebrate Cucumaria echinata was analyzed. The established sequence showed that CEL-IV comprises 157 amino acid residues with a molecular mass of 17,098 Da (without disulfide bonds). From comparison with other proteins, CEL-IV was apparently homologous with the C-type lectin family. The identity was relatively high with a sea cucumber (Stichopus japonicus) lectin SJL-I (40.0%) and a sea urchin (Anthocidaris crassispina) lectin echinoidin (32.6%). In CEL-IV, one interchain and two intrachain disulfide bonds were identified. Interestingly, one of the two intrachain disulfide bonds that were highly conserved among the other C-type lectins was missing, suggesting that this might be a characteristic feature of C-type lectins in the Holothuroidea.