title: Characterization of the trimeric, self-recognizing Geodia cydonium lectin I.
abstract: A D-galactose-specific lectin I was extracted from the sponge Geodia cydonium and purified by affinity chromatography. The molecular weight of lectin I as determined by high-pressure liquid gel chromatography, was found to be 36500 +/- 1300. Disc gel electrophoresis in the presence and in the absence of sodium dodecyl sulfate showed that lectin I is a trimer composed of three different subunits (Mr: 13800, 13000 and 12200); two of the three subunits are linked by one disulfide bond. Isoelectric focusing gave a pI of 5.6 for the native molecule and a pI of 4.4 and of 7.4 for the subunits. The three subunits carry carbohydrate side chains, composed of D-galactose (94%) and of arabinose (5%). Based on experiments with lectins, the terminal D-galactose residues are bound by beta 1 leads to 6 and/or beta 1 leads to 4 glycosidic linkages. The Geodia lectin I contains, besides two carbohydrate recognition sites, at least one receptor site for a second lectin I molecule.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D055598:Chemical Phenomena; D002621:Chemistry; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D037102:Lectins / Q000302:isolation & purification*; D008970:Molecular Weight; D011161:Porifera / Q000032:analysis*
chemical_list: D000596:Amino Acids; D002241:Carbohydrates; D037102:Lectins