Negative cooperativity in the human bradykinin B2 receptor

A human kidney bradykinin (BH) B-2, receptor cDNA was transfected in CHO-KI cells to establish cell lines that express stably and at high density a receptor exhibiting B-2, receptor properties in terms of coupling to cell signaling effecters, desensitization, and internalization. A cell line with a density of 1.3 x 10(6) receptors/cell allowed us to carry out a detailed study of BK-receptor interaction over a wide range of BK concentrations. A model assuming that BK binds to two receptor affinity states (depending on guanine nucleotide-sensitive coupling) was not sufficient to account for the kinetics of EE binding. Equilibrium kinetic analysis and studies of the effects of receptor occupancy by agonists or antagonists on the kinetics of BH-receptor complex dissociation revealed features typical of negative cooperative binding. The negative cooperativity phenomenon was also observed in isolated membranes in both the presence and absence of guanine nucleotide, Thus, following the interaction with Bg, B-2, receptor molecules likely interact with each other, resulting in an acceleration of bound ligand dissociation and a decrease in the apparent affinity of the receptor for BR This phenomenon can participate in the desensitization process.