Purification and Characterization of the Hemagglutinin Present in Potatoes

Abstract

Summary A procedure is described for the isolation of the hemagglutinin found in potatoes. Evidence is presented that this procedure results in a highly purified preparation. The lectin is a nonspecific agglutinin with optimal activity at 4°C, and is reversibly bound to the red cells during agglutination. It is a basic glycoprotein with a sedimentation constant of 2.1 S, containing 12.5% nitrogen and 5.2% carbohydrate. A 0.1% solution of the lectin has a specific absorbance (K2780 Å) of 0.962 per mg-cm, and an agglutination dilution titer of 1:104. Thus agglutination is detectable at a lectin concentration as low as 0.1 γ/ml. The lectin is shown to contain only one type of sugar, tentatively identified as arabinose. Amino acid analysis shows a preponderance of acidic amino over basic amino acids even though the lectin behaves as a basic molecule. This discrepancy is not easily explained by hydrolytic loss alone. The alternative possibility is presented that the sugar molecule is attached to the protein moiety by ester linkage to the free carboxyl groups of aspartyl and glutamyl residues, thereby mitigating their contribution to the net charge of the molecule. The mechanism involved in the agglutinating activity of the potato lectin is briefly discussed.