Printed in U.S.A. Kinetics of Receptor-mediated Binding of Tropoelastin to Ligament Fibroblasts”

Soluble 129-labeled tropoelastin bound to confluent cultures of bovine ligamentum nuchae fibroblasts and to fibroblast plasma membrane preparations in a time-dependent, saturable, and reversible manner. Scat-chard analysis indicates that there are approximately 2 X 10 ’ binding sites/cell with a binding efficiency (Ka) of 8 X lo- ’ M. Binding of tropoelastin to cells and membranes reached equilibrium by 90 min and was reversible with 50 % of specifically bound material re-leased by 40 min. Specific binding o f tropoelastin to cells pre-treated with dilute trypsin solutions was re-duced significantly when compared with controls. Four polypeptides of estimated molecular masses of 67, 61, 55, and 43 kDa were obtained from detergent extracts of plasma membranes by elution affinity chromatog