Human serum albumin. Spectroscopic studies of binding and proximity relationships for fatty acids and bilirubin

C. B. Berde, B. S. Hudson, R. D. Simoni, L. A. Sklar

Research output: Contribution to journalArticle

207 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)391-400
Number of pages10
JournalJournal of Biological Chemistry
Volume254
Issue number2
StatePublished - Jan 1 1979

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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