Competitive inhibition of [3H]dexamethasone binding to mammary glucocorticoid receptor by leupeptin

• Published in: Proceedings of the Society for Experimental Biology and Medicine Vol. 184; no. 3; p. 295
• Main Authors: Hsieh, L C, Su, C, Markland, Jr, F S
• Format: Journal Article
• Language: English
• Published: United States 01.03.1987
• Subjects: Animals; Binding, Competitive; Centrifugation, Density Gradient; Dexamethasone - antagonists & inhibitors; Dexamethasone - metabolism; Female; Goats; Kinetics; Leupeptins - metabolism; Mammary Glands, Animal - metabolism; Oligopeptides - metabolism; Receptors, Glucocorticoid - isolation & purification; Receptors, Glucocorticoid - metabolism
• ISSN: 0037-9727
• DOI: 10.3181/00379727-184-42482

The inhibitory effect of leupeptin on [3H]dexamethasone binding to the glucocorticoid receptor from lactating goat mammary cytosol has been studied. Leupeptin (10 mM) caused a significant (about 35%) inhibition of [3H]dexamethasone binding to glucocorticoid receptor. Binding inhibition is further increased following filtration of unlabeled cytosolic receptor through a Bio-Gel A 0.5-m column. Binding inhibition was partially reversed by monothioglycerol at 10 mM concentration. A double reciprocal plot revealed that leupeptin appears to be a competitive inhibitor of [3H]dexamethasone binding to the glucocorticoid receptor. Low salt sucrose density gradient centrifugation revealed that the leupeptin-treated sample formed a slightly larger (approximately 9 S) receptor complex (leupeptin-free complex sediments at 8 S).