The amino-acid sequence of multiple lectins of the acorn barnacle Megabalanus rosa and its homology with animal lectins

The amino-acid sequence of a lectin isolated from the coelomic fluid of the acorn barnacle Megabalanus rosa has been determined. The lectin (Mr 140,000) is a multimeric protein whose subunit consists of 173 amino acids and one carbohydrate chain attached to Asn-39. The amino-acid sequence was determined by the manual sequencing of peptides derived from the protein by digestion with Staphylococcus aureus V8 proteinase, lysine endopeptidase and chymotrypsin, as well as fragments produced by cleavage with cyanogen bromide. The amino-acid sequence of the lectin was compared with the sequence of one (Mr 64,000) of the multiple lectins of M. rosa. They are distinct molecules in spite of a significant homology in their amino-acid sequences. The amino-acid sequence includes some regions homologous to those in other invertebrate lectins, such as sea urchin and flesh fly lectins, and vertebrate lectins. This is the first report to show the amino-acid sequence of multiple lectins isolated from an invertebrate.