title: Isolation and partial characterization of membrane protein constituents of human neutrophil receptors for chemotactic formylmethionyl peptides.
abstract: Plasma membranes of human neutrophils were solubilized in buffer containing a nonionic detergent and applied to a formylmethionylleucylphenylalanine (fMet-Leu-Phe)-Sepharose column that was washed and eluted with the chemotactic peptide fMet-Leu-Phe. Analysis of the eluate by filtration on Bio-Gel P150 in sodium dodecyl sulfate (NaDodSO4) buffer and by NaDodSO4-polyacrylamide gel electrophoresis revealed three predominant membrane proteins of approximate molecular weight 94 000 (MP-1), 68 000 (MP-2), and 40 000 (MP-3), of which MP-2 accounted for 74--93% of the total protein. Purified MP-1 and MP-2 contained an above average content of hydrophobic amino acids, while MP-2 and MP-3 had an above average content of acid and/or amide amino acids and a below average content of basic amino acids. MP-2 and MP-3, but not MP-1, bound [3H]fMet-Leu-Phe in equilibrium dialysis chambers. Both MP-2 and MP-3 exhibited high-affinity sites with a valence of 0.2--0.3 and mean KA values of 9 x 10(8) and 2 x 10(7) M-1, respectively, and low-affinity sites with a valence of 0.3--0.5 and mean KA values of 3 x 10(7) and 2 x 10(6) M-1 (n = 3). The specificity of the binding of fMet-Leu-Phe was suggested by the failure of MP-2 and MP-3 to bind lipid chemotactic factors and to adhere to a Sepaharose column to which had been coupled chemotactic fragments of the fifth component of complement. A series of synthetic formylmethionyl peptides exhibited the same rank order of potency as inhibitors of the binding of [3H]fMet-Leu-Phe by MP-2 and as stimuli of neutrophil chemotaxis. Membrane proteins isolated by fMet-Leu-Phe-Sepharose affinity chromatography may represent constituents of specific human neutrophil receptors for chemotactic peptides.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002462:Cell Membrane / Q000737:chemistry; D002630:Chemotactic Factors / Q000302:isolation & purification*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008565:Membrane Proteins / Q000302:isolation & purification*; D008970:Molecular Weight; D009239:N-Formylmethionine / Q000031:analogs & derivatives; D009240:N-Formylmethionine Leucyl-Phenylalanine; D009504:Neutrophils / Q000737:chemistry*; D009842:Oligopeptides; D011956:Receptors, Cell Surface / Q000302:isolation & purification*; D044042:Receptors, Formyl Peptide
chemical_list: D000596:Amino Acids; D002630:Chemotactic Factors; D008565:Membrane Proteins; D009842:Oligopeptides; D011956:Receptors, Cell Surface; D044042:Receptors, Formyl Peptide; D009239:N-Formylmethionine; D009240:N-Formylmethionine Leucyl-Phenylalanine