Reaction of lectins with human erythrocytes: IV. Details of adsorption and desorption of ConA

• Published in: Experimental cell research Vol. 105; no. 1; pp. 151 - 157
• Main Authors: Schnebli, H.P., Lustig, A., Zulauf, M., Winterhalter, K.H., Joss, U.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.03.1977
• Subjects: Agglutination - drug effects; Binding, Competitive; Concanavalin A - analogs & derivatives; Concanavalin A - blood; Concanavalin A - pharmacology; Erythrocytes - metabolism; Humans; In Vitro Techniques; Molecular Weight; Protein Binding; Protein Conformation; Spectrophotometry, Ultraviolet; Temperature; Time Factors; Ultracentrifugation
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1016/0014-4827(77)90161-6

The ConA molecule is in a concentration and temperature-dependent dimer-tetramer equilibrium: low temperature and concentrations favor the dimeric, while temperatures above 15°C and higher concentrations favor the tetrameric form. In solution the association-dissociation equilibrium responds rapidly to changes in temperature. ConA bound to erythrocytes at low temperature (dimeric) rapidly associates to the tetramer when the temperature is raised. In contrast, ConA bound to erythrocytes in the tetrameric form (at high temperature) dissociates only slowly into bound and released dimers after lowering of the temperature. This is interpreted to reflect a conformational change in the ConA molecule when bound to cell receptors which interferes with the cold-induced dissociation into ConA dimers. A conformational change of this nature accounts for the fact that at low concentrations, ConA binding shows positive cooperativity at 24°C and 37°C but not at 0°C where the molecule exists predominantly as dimer. Cell agglutination by ConA shows the kind of temperature dependence expected for any chemical reaction and is not blocked at 0°C. Dimeric ConA therefore can function as agglutinin.