Cooperative binding of concanavalin a to thymocyte membrane vesicles augments uptake of α-aminoisobutyrate

(1) Membrane vesicles from rabbit thymocytes accumulate α‐aminoisobutyrate in the presence of 0.1 M NaCl. Uptake is 1/2 maximal after about 2 min and reaches a plateau value (61 pmoles/mg protein) after 30 min. (2) Up to 25 μg concanavalin A/ml, binding of the lectin describes a sigmoid curve indicative of a cooperative process. (3) At lectin concentrations up to 8 μg/ml, lectin binding enhances the uptake of α‐aminoisobutyrate (maximally 30%).