Ligand-induced formation of the leukotriene B4 receptor-G protein complex of human polymorphonuclear leukocytes

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Abstract
The components of the polymorphonuclear leukocyte (PMNL) receptor for leukotriene B4 (LTB4) were examined by Sephacryl S‐300 exclusion chromatography of PMNL membrane proteins, which were solubilized before and after the binding of [3H] LTB4. When the PMNL membranes were solubilized in 3‐[(3‐cholamidopropyl)‐dimethylammonio]‐1‐propanesulfonate (CHAPS) and filtered on Sephacryl S‐300 prior to addition of [3H] LTB4, the binding activity was associated with a 65 kD protein. In contrast, the radioactivity of [3H] LTB4 bound to PMNL membranes prior to solubilization was recovered predominately with a 140 kD protein. When PMNL membranes had been pretreated with pertussis toxin, but not cholera toxin, before the addition of LTB4 and subsequent solubilization, radioactivity was recovered predominately with the 65 kD protein. The addition of guanylylimidodiphosphate (GMP‐PNP), a nonhydrolyzable derivative of guanosine triphosphate (GTP), to PMNL membrane receptors bearing [3H] LTB4 either prior to or after CHAPS solubilization reduced the yield of the 140 kD presumed LTB4 receptor protein‐G protein complex. That the maximum specific binding of [35S] guanosine‐5′‐0‐3‐thiotriphosphate (GTP‐gammaS) to LTB4‐binding proteins in the Sephacryl S‐300 effluent corresponded to the 140 kD protein supported the presence of a G protein in the LTB4 receptor complex.