Ligand‐induced formation of the leukotriene B 4 receptor‐G protein complex of human polymorphonuclear leukocytes

The components of the polymorphonuclear leukocyte (PMNL) receptor for leukotriene B 4 (LTB 4 ) were examined by Sephacryl S‐300 exclusion chromatography of PMNL membrane proteins, which were solubilized before and after the binding of [3H] LTB 4 . 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] LTB 4 , the binding activity was associated with a 65 kD protein. In contrast, the radioactivity of [3H] LTB 4 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 LTB 4 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] LTB 4 either prior to or after CHAPS solubilization reduced the yield of the 140 kD presumed LTB 4 receptor protein‐G protein complex. That the maximum specific binding of [35S] guanosine‐5′‐0‐3‐thiotriphosphate (GTP‐gammaS) to LTB 4 ‐binding proteins in the Sephacryl S‐300 effluent corresponded to the 140 kD protein supported the presence of a G protein in the LTB 4 receptor complex.