Isolation and characterization of a galactose-specific carbohydrate binding protein from human lymphoblastic cells

A carbohydrate binding protein of Mr = 32,000 (CBP 32) has been isolated from detergent extracts of human B and T lymphoblastoid cells. CBP 32 binds specifically to glycoproteins containing asparagine-linked complex oligosaccharides, and can be eluted from a fetuin affinity matrix by beta-lactose. Binding is not thiol dependent, nor are divalent cations necessary for binding. Native CBP 32 appears to exist as a monomer, with a pI of 8.2. Purified CBP 32 can bind detergent, as shown by charge-shift electrophoresis, and thus appears to be an integral membrane protein.