Identification of a 148-kDa surface lectin from Giardia lamblia with specificity for alpha-methyl-D-mannoside

A lectin specific for alpha-methyl-D-mannoside was purified from the membrane extract of Giardia lamblia by a combination of gel filtration chromatography on Sephadex G-75 and Superose 6-HR 10/30. The homogeneity of the lectin was established by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecular mass of the native protein was 148 kDa. The lectin agglutinated rabbit erythrocytes in the presence of Ca2+ at 37 degrees C and pH 7.0. The maximum activity of the lectin was obtained after trypsin treatment. The inhibition study clearly suggests that the binding site of the lectin recognizes alpha-methyl-D-mannoside as the immunodominant sugar.