Galect1ns from ectothermic vertebrates and invertebrates: molecular structure and carbohydrate-binding specificities

Galectins are a family of soluble β-gaiactoside-binding lectins present in vertebrates, invertebrates, and fungi, which exhibit a typical motif of conserved amino acids in their carbohydrate recognition domain(s) (CRDs). In order to gain insight on galectin structure-function relationships we characterized the molecular organization and carbohydrate specificity of galectins from ectothermic vertebrates (amphibians and fish) and invertebrates (tunicates, echinoderms and sponges). On SDS-PAGE under reducing conditions, galectins from most species appeared as multiple bands ranging from 14.5 kDa to 67 kDa. Galectins from amphibians and fish species exhibited galectin-1-like "conserved" type CRDs (Ahmed & Vasta, 1994 Glycobiology 4: 545-549), as determined from their primary structures and carbohydrate-binding specificities. The C. elegans 16 kDa galectin exhibits a "variable" type CRD with a novel carbohydrate specificity. The structural basis of the carbohydrate specificities characterized was elucidated through the determination of the structures or homology modeling.