Mammalian fetuin-binding proteins sarcolectin, aprotinin and calcyclin display differences in their apparent...

The interferon antagonist sarcolectin, the protease inhibitor aprotinin and calcyclin whose expression is regulated by growth stimulation in quiescent fibroblasts display sialic acid-dependent binding to fetuin, visualized by solid-phase assays using biotinylated fetuin. The potential functional importance of this property prompted its comparative characterization with an array of neutral or negatively charged sugars, sulfated polysaccharides and sialoglycoproteins as inhibitors of binding of biotinylated fetuin to the immobilized proteins. The results revealed that this activity of sarcolectin and calcyclin is nearly unaffected by charge-free carbohydrates in contrast to aprotinin, calcyclin exhibits a notable affinity for Neu5Gc and together with aprotinin for phosphorylated sugars, and that sarcolectin's binding is affected to the highest extent by sulfated sugars relative to aprotinin and calcyclin.