Human serum albumin (HSA), domain IIA (HSA-DIIA)

Human serum albumin (HSA) is the most abundant protein in human plasma, essential for maintaining colloidal osmotic pressure and transporting a wide array of ligands [UniProt, 2024]. Domain IIA, which houses the well-known Sudlow's site I (also called the warfarin binding site), is a major drug-binding region characterized by a large hydrophobic pocket [PMC, 2014]. This domain typically accommodates bulky heterocyclic anions, including therapeutic agents such as the anticoagulant warfarin and various non-steroidal anti-inflammatory drugs [PubMed, 2008]. Beyond its transport function, Domain IIA plays a role in the innate immune system by binding and neutralizing bacterial toxins, such as those from Clostridioides difficile [FEBS, 2024]. It also exhibits pseudo-enzymatic activities, including esterase and aldolase-like functions, which can influence the metabolism of bound substances [MDPI, 2023]. In clinical settings, HSA is administered to treat conditions like hypovolemia and hypoalbuminemia, but its binding domains are critical for understanding drug pharmacokinetics [Wikipedia, 2024]. Competition for the Domain IIA binding site is a major source of drug-drug interactions, as the displacement of one drug by another can significantly increase the free, active fraction in the blood [PMC, 2014]. Structural modifications to this domain, such as glycation in patients with diabetes, can impair its binding affinity and overall physiological performance [Wikipedia, 2024]. Safety concerns associated with HSA therapy include fluid overload and rare but serious reactions like transfusion-related acute lung injury [Frontiers in Pharmacology, 2024].

Other names

Sudlow's site IWarfarin binding siteSubdomain IIASite I

Reversible binding for systemic transport and distribution; sequestration and neutralization of bacterial toxins; allosteric modulation of other binding sites.