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Binding of platelet activating factor to albumin
K L Clay1, C Johnson, P Henson
1National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206.
Biochimica Et Biophysica Acta
|October 1, 1990
Summary
Platelet activating factor (PAF) binds to albumin at four sites, with a dissociation constant of 1.10(-7) M. This binding suggests the albumin-PAF complex, not free PAF, may be the active form.
Area of Science:
- Biochemistry
- Pharmacology
- Lipid Research
Background:
- Platelet activating factor (PAF) is a phospholipid with significant biological activity.
- Understanding PAF's interaction with plasma proteins like albumin is crucial for its biological function.
- Previous methods for measuring PAF binding were limited by the lipid's physical properties.
Purpose of the Study:
- To accurately quantify the binding of platelet activating factor (PAF) to albumin.
- To determine the binding affinity and stoichiometry of the PAF-albumin interaction.
- To investigate the hypothesis that the albumin-PAF complex is the biologically active form of PAF.
Main Methods:
- Utilized ultracentrifugation to create an albumin gradient.
- Developed a method to measure both free and albumin-bound concentrations of PAF.
- Applied equilibrium dissociation constant calculations to determine binding parameters.
Main Results:
- Successfully measured free and albumin-bound PAF concentrations.
- Demonstrated that PAF binds to albumin at four distinct binding sites.
- Determined the average equilibrium dissociation constant for PAF-albumin binding to be 1.10(-7) M.
Conclusions:
- PAF exhibits specific binding to albumin.
- The stoichiometry suggests multiple binding sites on albumin for PAF.
- The findings support the hypothesis that the albumin-PAF complex is the biologically relevant form of PAF, rather than free PAF.