AGGLUTININ AND CELL AGGLUTINATION IV.CHARACTERIZATION OF CONCANAVALIN A RECEPTORS ON HEPATOMA CELLS
摘要
The Scatchard plots of the radioreceptor data for Con A receptors with normalmice liver cells and for the same receptors with ascitic hepatoma (Hop A)cells are diff-erent.In the case of normal cells,the plot is linear,but with Hep A it is an upwardconcave curve.Using heat inactivation,dilution and dissociation tests,we concludethat the upward concave curve is not due to negative cooperation or site-site interactionof the receptors but indicates rather the presence of two kinds of receptors with diff-erent degrees of affinity.The high affinity receptor disappears on heating at 50℃ for 20 minutes,whilethe lower affinity receptor remains unchanged.The number of Con A receptors percell is essentially the same before and after heating,indicating therefore,that thehigh affinity receptors have not been destroyed but have been changed to low affinityreceptors.Furthermore,the decrease of the agglutinability of Hop A cells is parallelto the heat inactivation of the high affinity Con A receptors.The heat inactivation of Con A receptor occurs abruptly at 50℃.At 48℃,theactivity of the high affinity receptor is preserved,though with some what loweractivity,while at 50℃ the activity is entirely lost.This sudden change is similar tothe phase transition of membrane phospholipids.Whether heat inactivation of thehigh affinity receptor is the result of denaturation of the receptor protein or that ofthe phase transition of membrane lipids remains a problem for further study.