TY - JOUR
T1 - Human serum albumin. Spectroscopic studies of binding and proximity relationships for fatty acids and bilirubin
AU - Berde, C. B.
AU - Hudson, B. S.
AU - Simoni, R. D.
AU - Sklar, L. A.
PY - 1979
Y1 - 1979
N2 - Binding and proximity relationships of hydrophobic ligands on human serum albumin have been studied using absorption, fluorescence, circular dichroism, and electron paramagnetic resonance spectroscopy. The ligands studied were bilirubin, two conjugated linear polyene fatty acids, cis-parinaric acid and cis-eleostearic acid, and three nitroxide derivatives of stearic acid with doxyl groups at positions 5, 10, and 12, respectively. Binding of polyene fatty acids was monitored by absorption peak shifts, induced circular dichroism, enhancement of fluorescence, and energy transfer between albumin's single tryptophanyl residue and the polyene chromophore. Induced circular dichroism studies indicate excitonic ligand-ligand interaction between bound fatty acids. Fluorescence enhancement of cis-parinaric acid was analyzed using a stepwise multiple equilibrium model, and six binding constants in the range 108 to 106 M-1 were obtained, in agreement with previous measurements for other fatty acids. The temperature dependence of the equilibrium constants indicates that the binding enthalpy is nearly zero. Fluorescence energy transfer was similary used to quantitate bilirubin binding to albumin. Energy transfer, nitroxide quenching of fluorescence, and electron paramagnetic resonance spectroscopy were used to elucidate binding geometries which support and extend proposed structural models for albumin. It is suggested that the first two fatty acids bind side-by-side in an antiparallel fashion in domain III of human serum albumin.
AB - Binding and proximity relationships of hydrophobic ligands on human serum albumin have been studied using absorption, fluorescence, circular dichroism, and electron paramagnetic resonance spectroscopy. The ligands studied were bilirubin, two conjugated linear polyene fatty acids, cis-parinaric acid and cis-eleostearic acid, and three nitroxide derivatives of stearic acid with doxyl groups at positions 5, 10, and 12, respectively. Binding of polyene fatty acids was monitored by absorption peak shifts, induced circular dichroism, enhancement of fluorescence, and energy transfer between albumin's single tryptophanyl residue and the polyene chromophore. Induced circular dichroism studies indicate excitonic ligand-ligand interaction between bound fatty acids. Fluorescence enhancement of cis-parinaric acid was analyzed using a stepwise multiple equilibrium model, and six binding constants in the range 108 to 106 M-1 were obtained, in agreement with previous measurements for other fatty acids. The temperature dependence of the equilibrium constants indicates that the binding enthalpy is nearly zero. Fluorescence energy transfer was similary used to quantitate bilirubin binding to albumin. Energy transfer, nitroxide quenching of fluorescence, and electron paramagnetic resonance spectroscopy were used to elucidate binding geometries which support and extend proposed structural models for albumin. It is suggested that the first two fatty acids bind side-by-side in an antiparallel fashion in domain III of human serum albumin.
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M3 - Article
C2 - 216673
AN - SCOPUS:0018413926
SN - 0021-9258
VL - 254
SP - 391
EP - 400
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 2
ER -