Human serum albumin (HSA) subdomain IB (HSA subdomain IB)

Human serum albumin (HSA) is the most abundant protein in human blood plasma, synthesized by the liver and essential for maintaining the oncotic pressure of the vascular system [1, 3]. It is a single-chain polypeptide organized into three homologous domains (I, II, and III), each subdivided into A and B subdomains. Subdomain IB is a distinct structural region that functions as a major binding site for various endogenous and exogenous ligands, most notably heme and certain heterocyclic drugs like lidocaine and bupivacaine [2, 4]. Beyond its role as a carrier protein for fatty acids and hormones, HSA acts as a significant extracellular antioxidant and pH buffer [3]. In clinical settings, HSA levels serve as critical biomarkers for nutritional status, liver function, and renal health. The binding affinity of subdomain IB is a key determinant in the pharmacokinetics of many drugs, as competition for this site can lead to increased free drug concentrations and potential toxicity [2]. Consequently, HSA is a primary consideration in drug design and the management of drug-drug interactions.

Other names

ALBAlbuminSerum albuminHeme-binding site of HSASudlow's site III (proposed)

Reversible binding and transport of endogenous and exogenous ligands in the circulatory system, which regulates the free fraction of drugs and their systemic distribution [2, 3].