Bovine serum albumin (BSA) (BSA)

Bovine serum albumin (BSA) is a 583-amino acid globular protein (UniProt: P02769) that serves as the primary carrier protein in bovine plasma and is widely used as a biochemical model for human serum albumin (HSA) due to their 76% sequence identity (Ghuman et al., 2005). Sudlow site 1, also known as the warfarin binding site or Site I, is a large, flexible hydrophobic pocket located within subdomain IIA of the protein's tertiary structure (Sudlow et al., 1975). This site primarily binds bulky heterocyclic anions and is characterized by a central hydrophobic zone surrounded by polar residues that stabilize ligand binding through hydrogen bonding and electrostatic interactions (PubChem CID: 16132389). Biologically, albumin is essential for maintaining the colloid osmotic pressure of blood and transporting endogenous substances such as long-chain fatty acids, bilirubin, and various hormones (StatPearls: Albumin). In pharmacology, Sudlow site 1 is a critical determinant of drug pharmacokinetics, as binding to this site limits the amount of free drug available to reach its intended therapeutic target. Interactions at this site are a major source of drug-drug interactions; for instance, the displacement of highly protein-bound drugs like warfarin can lead to increased toxicity. Consequently, BSA is an indispensable tool in drug discovery for evaluating the binding affinity and distribution profiles of new chemical entities.

Other names

BSASerum albuminSudlow site 1Warfarin binding siteSite ISubdomain IIA binding site

Bovine serum albumin acts as a transport protein that binds and carries various ligands, including drugs, in the circulatory system. Sudlow site 1 specifically facilitates the binding of bulky heterocyclic anions through hydrophobic and electrostatic interactions, thereby regulating the drug's free concentration, half-life, and systemic distribution (Sudlow et al., 1975; Ghuman et al., 2005).