S-TYPE LECTINS OCCUR ALSO IN INVERTEBRATES - HIGH CONSERVATION OF THE CARBOHYDRATE RECOGNITION DOMAIN IN THE LECTIN GENES FROM THE MARINE SPONGE GEODIA-CYDONIUM

The marine sponge Geodia cydonium contains several lectins. The main component, called lectin-1, is composed of three to four identical subunits. The subunits of the lectins were cloned from a cDNA library; two clones were obtained. From the deduced aa sequence of one clone, LECT-1, a mol. wt of 15 313 Da is calculated; this value is in good agreement with mass spectrometric analysis of 15 453 +/- 25 Da. The sequence of another clone, LECT-2, was analysed and the aa sequence was deduced (15 433 Da). The two subunits have a framework sequence of 38 conserved aa which are characteristic for the carbohydrate-binding site of vertebrate S-type lectins. Clustering of lectin sequences of various species following their pairwise comparison establishes a dendrogram, which reveals that the sponge lectin could be considered as the ancestor for vertebrate S-type lectins.