EFFECTS OF METAL-IONS ON THE BINDING-ACTIVITY OF THE HUMAN-LEUKOCYTE LEUKOTRIENE B-4 RECEPTOR

The specific binding of leukotriene B-4 to its receptor on human leuko cyte membranes was enhanced in a dose-dependent manner by metal ions. Mg2+ and Ca2+ mere the most potent followed by Mn2+ and Co2+. These di valent cations increased receptor density and did not affect the bindi ng affinity. Addition of the same divalent cations to a partially puri fied receptor prepared by precipitation with polyethylene glycol produ ced a greater effect, whereby both binding affinity and receptor densi ty were significantly increased. Zn2+ inhibited activity in both prepa rations by decreasing the density of receptors. In the membrane prepar ation, binding activity was decreased by Na+ and increased by K+, whil e Li+ had no effect. However, in the partially purified receptor prepa ration, these monovalent cations all increased the binding activity. O ur findings show that purification of the leukotriene Bq receptor modi fies its response to various monovalent and divalent cations, perhaps by removing certain cellular components involved in receptor regulatio n. (C) 1997 Academic Press.