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Correspondence of fatty acid and drug binding sites on HSA: A 2D NMR Study.

Biochemistry. 2013 Jan 29;

Authors: Krenzel ES, Chen Z, Hamilton JA


The ability of human serum albumin (HSA) to bind fatty acids (FA) in multiple sites has been revealed by many studies Here we characterize 9 individual binding sites and quantify their relative affinities by 2D NMR spectroscopy of 18-13C-oleic acid (OA) complexed with HSA. We probed site-specific FA binding by addition of: (i) different FA molar ratios to observe the order of filling and occupancy of binding sites; (ii) cyclodextrin as FA acceptor to observe the dissociation of FA; and (iii) drugs that are known to bind to low affinity FA sites. At 1:1 and 2:1 OA:HSA, 3 sites filled sequentially. These high affinity sites were well resolved from 1 medium and 5 lower affinity sites observed at 3:1- 4:1 OA:HSA. At the 4:1 ratio, the highest affinity-binding sites had similar equilibrium constants, with the others having constants ~5 times lower. Methyl-β-cyclodextrin extracted OA from individual sites, in the reverse order of filling. Three primary drug sites, Sudlow's Drug Sites 1 and 2, and FA Site 6, were identified by drug competition as lower affinity FA sites. Our strategies permit site-specific characterization of drug binding, and provide a sensitive probe of the mutual effects of FA and ligand binding.

PMID: 23360066 [PubMed - as supplied by publisher]