AMINO-ACID-SEQUENCE OF A LECTIN FROM THE SEA-CUCUMBER, STICHOPUS-JAPONICUS, AND ITS STRUCTURAL RELATIONSHIP TO THE C-TYPE ANIMAL LECTIN FAMILY

The complete amino acid sequence of SJL-I, a lectin from the sea cucum ber, Stichopus japonicus, was determined by sequence analysis of pepti des derived on enzymatic and chemical fragmentation of the protein. SJ L-I consists of 143 amino acid residues and its molecular mass was cal culated to be 15,837 Da. Comparison of the sequence of SJL-I with a da tabase revealed that SJL-I exhibits apparent homology with C-type lect ins, especially with those of marine invertebrates. The highest homolo gy (identity 28.6%) was found with echinoidin, a lectin from the sea u rchin, Anthocidaris crassispina. Comparison of the sequence of SJL-I w ith those of other C-type lectins indicated that the conserved amino a cids are relatively abundant in the C-terminal half of their carbohydr ate-recognition domains (CRDs), that can be considered to be involved in binding with Ca2+ as well as carbohydrates.