LG/LNS domains: multiple functions - one business end?

The three-dimensional structures of LG/LNS domains from neurexin, the lamin in alpha2 chain and sex hormone-binding globulin reveal a close structural relationship to the carbohydrate-binding pentraxins and other lectins, Howe ver, these LG/LNS domains appear to have a preferential ligand-interaction site distinct from the carbohydrate-binding sites found in lectins, and thi s interaction site accommodates not only sugars but also steroids and prote ins. In fact, the LG/LNS domain interaction site has features reminiscent o f the antigen-combining sites in immunoglobulins. The LG/LNS domain present s an interesting case in which the fold has remained conserved but the func tional sites have evolved; consequently, making predictions of structure-fu nction relationships on the basis of the lectin fold alone is difficult.