Characterization of benzodiazepine binding site on human α1-acid glycoprotein using flunitrazepam as a photolabeling agent

The binding of flunitrazepam (FNZP) by human alpha(1)-acid glycoprotein (hAGP) and the relationships between the extent of drug binding and desialylation and the genetic variants of hAGP were examined. The photolabeling specificity of [H-3]FNZP was confirmed by findings in which other hAGP-binding ligands inhibited the formation of covalent bonds between [H-3]FNZP and hAGP. The photolabeling of asialo-hAGP suggested that sialic acid does not involve in the binding of [H-3]FNZP. No difference in the labeling could be found between the F1*S variants and A variant. Similarly, FNZP did not show a difference in binding affinity to the two genetic variants of hAGP. Sequence. analysis of the photolabeled peptide indicated a sequence corresponding to Tyr91-Arg105 of hAGP. (c) 2005 Elsevier B.V. All rights reserved.