Ligand binding, albumin sites

J. R. Brown, R Shockley, Serum Albumin Structure and Characterization of Its Ligand Binding Sites , in Lipid-Protein Interactions , Eds. P. C. Jost, O. H. Griffith, Wiley, New York, 1982, Vol. 1, p. 25-68. 

Fig. 21. Illustration summarizing the various ligand-binding sites on serum albumin. The asterisks denote binding sites that can be inferred all others have been determined crystallographically.

The albumin molecule has different binding sites for anionic and cationic ligands, but van der Waals forces also contribute (p. 58). The extent of binding correlates with drug hydrophobicity (repulsion of drug by water). 

Serum albumin has two primary hydrophobic binding sites, known as site I and site II, which are located in domains IIA and IIIA, respectively. Bulky heterocyclic anions with a centered charge are characteristic site I ligands, whereas site II ligands are in general aromatic compounds with a peripherally located charge if any (37). 

Serum albumin circulates in the blood stream transporting essential nutrients such as fatty acids to peripheral tissue. Transported molecules, called ligands, often have a special affinity for selected binding sites on proteins and nucleic acids. In this experiment, the dynamics of ligand-protein interactions will be explored with the binding of the dye phenol red to bovine serum albumin. The technique of gel filtration will be used to separate the dye-protein complex. Data will be analyzed in order to construct binding curves. 

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