title: Binding of platelet activating factor to albumin.
abstract: Binding of platelet activating factor (1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine) to albumin is an important facet of the biological activity of this phospholipid. Measurement of that binding has been hampered by the physical nature of the lipid, which made estimation of the free and bound concentrations difficult. With the use of ultracentrifugation to generate an albumin gradient and to produce a region free of protein, the successful measurement of free PAF and PAF bound to albumin was accomplished. This study has demonstrated that PAF binds to albumin at four binding sites and that the average equilibrium dissociation constant for this binding is 1.10(-7) M. Consideration of these data has led to the hypothesis that the receptor active form of PAF is the albumin-PAF complex, rather than free PAF.
authors.affiliation: National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206.
authors.forename: K L
authors.initials: KL
authors.lastname: Clay
authors.forename: C
authors.initials: C
authors.lastname: Johnson
authors.forename: P
authors.initials: P
authors.lastname: Henson
mesh_terms: D006801:Humans; D007700:Kinetics; D010972:Platelet Activating Factor / Q000737:chemistry / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism*; D014461:Ultracentrifugation
chemical_list: D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D012709:Serum Albumin; C039351:platelet activating factor receptor