György Mády

Selective binding interactions of deramciclane to the genetic variants of human α1-acid glycoprotein

BACKGROUND alpha(1)-Acid glycoprotein (AGP) plays a decisive role in the serum protein binding of several drugs.Genetic variants of AGP have different ligand binding properties. The binding of deramciclane (DER), a chiral anxiolytic agent, has been studied on A and F1/S genetic variants of AGP. METHODS The effects of DER and reference drugs on the binding of specific fluorescent and circular dichroism (CD) probes of AGP were determined. Dicumarol (DIC) binding was measured by CD and equilibrium dialysis. RESULTS DER effectively displaced probes bound to variant A, while it was less effective at displacing probes bound to variant F1/S. DER increased the binding and inverted the induced CD spectrum of DIC in the solution of variant F1/S. This phenomenon could not be brought about by the enantiomer of DER. CONCLUSION DER has high-affinity binding (K(a)> or =2x10(6) M(-1)) to variant A, while its binding to the variant F1/S is about thirty times weaker. During simultaneous binding of DER and DIC to variant F1/S a ternary complex having about four times higher affinity is formed, in which the opposite chiral conformation of DIC is favored. GENERAL SIGNIFICANCE The binding interactions found prove that AGP can simultaneously accommodate different ligand molecules. Even weakly bound ligands can provoke unexpected allosteric protein binding interactions.

Investigation of Macromolecules in Wines by Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was applied to the characterization of the protein content of wines. It has been established that this technique is applicable for this purpose even without sophisticated sample preparation. Direct structural information—presence of glycoproteins—was obtained from the MALDI spectra and was supported by an enzymatic degradation experiment. On the basis of the MALDI spectra it was possible to distinguish two different wines and a correlation was found between peak intensity ratios and the time of harvest.

Characterization of binding mode of imatinib to human α1-acid glycoprotein

Imatinib (IMT) is a selective tyrosine kinase inhibitor, used in the treatment of chronic myeloid leukemia and gastrointestinal stromal tumors. Its strong plasma protein binding was found to belong to the F1*S genetic variant of α(1)-acid glycoprotein (AGP). In this work, comparative AGP binding studies were performed with IMT fragment molecules to reveal which parts of the molecule are important in the high-affinity interaction provoking specific spectral changes. Molecular modeling calculations indicated that IMT docked into the X-ray structure of AGP/F1 adopts a bent, compact conformation. This binding mode is similar to those found in its complexes with some low-affinity kinases and a quinone reductase, being strikingly different from the extended conformation of IMT in its high-affinity kinase targets.