GALECTIN-4 AND GALECTIN-6 ARE 2 CLOSELY-RELATED LECTINS EXPRESSED IN MOUSE GASTROINTESTINAL-TRACT

Galectins are a family of carbohydrate-binding proteins that share a c onserved sequence and affinity for beta-galactosides. Some, such as ga lectin-1, are isolated as dimers and have a single carbohydrate recogn ition domain (CRD) in each monomer, whereas others, such as galectin-4 , are isolated as monomers and have two CRDs in a single polypeptide c hain. In the course of studying mouse colon mRNA for galectin-4, we de tected a related mRNA that encodes a new galectin that also has two CR Ds in a single peptide chain. The new galectin, galectin-6, lacks a 24 -amino acid stretch in the link region between the two CRDs that is pr esent in galectin-4. Otherwise, these two galectins have 83% amino aci d identity. Expression of both galectin-4 and galectin-6 is confined t o the epithelial cells of the embryonic and adult gastrointestinal tra ct. Galectin-4 is expressed at about equal levels in colon and small i ntestine but much less in stomach, whereas galectin-6 is expressed at about equal levels throughout the gastrointestinal tract.