In this thesis, the lectin site of the molecular chaperone calreticulin is characterized by analyzing key residues required for oligosaccharide binding. Knowledge of the lectin site of calreticulin's homolog calnexin allowed for the identification of six corresponding calreticulin residues that were then individually mutated. Mutations at four residues completely abolished oligosaccharide binding, suggesting that calreticulin's lectin site is largely similar to calnexin's lectin site. Comparison of oligosaccharide-binding deficient mutants to wild type calreticulin with respect to resistance to protease digestion and ability to bind the thiol oxidoreductase ERp57 showed that the mutants were structurally similar to wild type calreticulin. Only oligosaccharide binding was disrupted by the mutations. In vitro aggregation assays determined that the mutants suppressed the aggregation of a non-glycosylated substrate like wild type calreticulin, but were substantially impaired in aggregation suppression of a glycosylated substrate, thus illustrating the importance of the lectin site for interacting with glycosylated substrates.