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Influence of ligand binding on structure and thermostability of human α1‐acid glycoprotein

Ligand binding of neutral progesterone, basic propranolol, and acidic warfarin to human α1‐acid glycoprotein (AGP) was investigated by Raman spectroscopy. The binding itself is characterized by a uniform conformational shift in which a tryptophan residue is involved. Slight differences corresponding to different contacts of the individual ligands inside the β‐barrel are described. Results are compared with in silico ligand docking into the available crystal structure of deglycosylated AGP using quantum/molecular mechanics. Calculated binding energies are −18.2, −14.5, and −11.5 kcal/mol for warfarin, propranolol, and progesterone, respectively. These calculations are consistent with Raman difference spectroscopy; nevertheless, minor discrepancies in the precise positions of the ligands point to structural differences between deglycosylated and native AGP. Thermal dynamics of AGP with/without bounded warfarin was followed by Raman spectroscopy in a temperature range of 10–95 °C and analyzed by principal component analysis. With increasing temperature, a slight decrease of α‐helical content is observed that coincides with an increase in β‐sheet content. Above 45 °C, also β‐strands tend to unfold, and the observed decrease in β‐sheet coincides with an increase of β‐turns accompanied by a conformational shift of the nearby disulfide bridge from high‐energy trans‐gauche‐trans to more relaxed gauche‐gauche‐trans. This major rearrangement in the vicinity of the bridge is not only characterized by unfolding of the β‐sheet but also by subsequent ligand release. Hereby, ligand binding alters the protein dynamics, and the more rigid protein–ligand complex shows an improved thermal stability, a finding that contributes to the reported chaperone‐like function of AGP. Copyright © 2015 John Wiley & Sons, Ltd.

  • α1‐Acid glycoprotein (AGP) has a uniform structural rearrangement upon ligand binding.
  • The order of binding strength is warfarin > propranolol > progesterone.
  • Ligands buried inside the β‐barrel make AGP more rigid and increase thermal stability.
  • Relaxation of an S–S bridge points to a transition of β‐sheet to β‐turn in its vicinity.
  • The role of the carbohydrate moiety cannot be omitted in forming the structure of AGP.

Authors:   Vladimír Kopecký, Rüdiger Ettrich, Tomáš Pazderka, Kateřina Hofbauerová, David Řeha, Vladimír Baumruk
Journal:   Journal of Molecular Recognition
Year:   2015
Pages:   n/a
DOI:   10.1002/jmr.2496
Publication date:   24-Sep-2015
Facts, background information, dossiers
  • stability
  • Rearrangement
  • propranolol
  • progesterone
  • Wiley
  • thermostability
More about Wiley
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