The prickly lettuce agglutinin. I. Isolation from leaves of the prickly lettuce plant (Lactuca scariole).

An agglutinin has been isolated from leaves of the prickly lettuce plant (Lactuca scariole). The prickly lettuce agglutinin (PLA) agglutinates erythrocytes of the mouse and rat, and binds to, but does not agglutinate erythrocytes of other species. PLA can be precipitated from crude plant extracts by cold acetone and ammonium sulfate treatment, is sensitive to proteolytic enzyme activity, and contains carbohydrate residues, suggesting that it is a glycoprotein. The agglutinin has a molecular weight of approximately 84,000 as determined by SDS-PAGE studies. The receptor for PLA has not been elucidated but may involve, in part, sialic acid residues.