Interaction of human plasma low density lipoprotein with concanavalin A and with ricin.

Native human plasma low density lipoprotein (LDL) interacts with concanavalin A but not with ricin; apOLDL reacts with both lectins. Each reaction is inhibited by the appropriate lectin-specific carbohydrate. The "receptors" on LDL for these two lectins are not destroyed by digestion by proteolytic enzymes. Peptide hydrolysis does not influence the reactivity of LDL toward concanavalin A. It does, however, substantially enhance the ability of the lipoprotein to interact with ricin. The data strongly suggest that the carbohydrate protion of a glycoprotein component of LDL is bound at the saccharidespecific active site on the lectin.