Binding of the adhesive protein complex (LFA-1/Mac-1/p150,95) to concanavalin A.

At least 30 proteins from human PMNL plasma membranes capable of binding concanavalin A (Con A), can be identified after surface labeling with 125I and subsequent sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Immunoprecipitation of the labeled proteins after solubilization in non-ionic detergents, with monoclonal antibodies (MAbs) directed against a family of leukocyte membrane proteins (LFA-1, Mac-1, p150,95, and the beta subunit these glycoproteins share), indicated that Mac-1 and p150,95 were bound by Con A. Dissociation of the alpha and beta subunits with sodium dodecyl sulfate, electrophoresis, transfer to nitrocellulose paper, and subsequent binding of these proteins by Con A demonstrated Con A retention by Mac-1-alpha, p150,95-alpha, and the common beta subunit. Affinity of Con A for LFA-1-alpha from human peripheral blood PMNL could not be confirmed by direct binding or electroblotting. Similar experiments in a patient deficient in LFA-1, Mac-1, p150,95, and the beta subunit confirmed that Mac-1-alpha and the beta subunit were important Con A-binding proteins.