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Author
López-Nieto Arespa, Blanca
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Abstract
Human serum albumin (HSA) is the most abundant plasma protein and a major factor in the pharmacokinetics of drugs, as the bioavailability of all molecules that travel through the blood circulation depends on their binding strength and kinetics to this ‘molecular sponge’.
HSA is a non-glycoprotein, one of the few secreted proteins which lacks carbohydrates and is the most abundant protein component of the blood plasma, with a concentration of 42g/L. It contributes 80% of the colloid osmotic pressure that provides the driving force to retain the fluid within blood vessels. In addition to the osmotic function, HSA provides a high-capacity reservoir to stabilize the concentration of the ligands.
The high total charge, potentially about 185 ions per molecule at pH 7, aids its solubility, and the many disulfide bonds, a feature of most extracellular proteins, contribute to its stability.
Since HSA is very large for NMR purposes (66.5 KDa) we have been focused on the third domain (DIII), which has been expressed in bacterial cells (E. coli) and purified. Nuclear magnetic resonance techniques (NMR) have been used to study the binding properties of HSA with oxyphenbutazone and propofol through Saturation Transfer Difference (STD) experiments. NMR data acquisition has already been achieved for the assignment part, but several questions remain concerning the cysteine binding pattern.
Moreover, a new software tool (TITAN) has been used to analyze titration experiments, from which structural, mechanistic, thermodynamic, and kinetic information can be extracted.
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