Journal of the American Society for Mass Spectrometry

, Volume 11, Issue 7, pp 606–614

Noncovalent associations of glutathione S-transferase and ligands: A study using electrospray quadrupole/time-of-flight mass spectrometry

Authors

  • Masaki Ishigai
    • Michael Barber Centre for Mass SpectrometryUMIST
    • Fuji Gotenba Research LabChugai Pharmaceutical Co. Ltd.
  • James I. Langridge
    • Micromass UK Ltd.
  • Robert S. Bordoli
    • Micromass UK Ltd.
    • Michael Barber Centre for Mass SpectrometryUMIST
Article

DOI: 10.1016/S1044-0305(00)00127-6

Cite this article as:
Ishigai, M., Langridge, J.I., Bordoli, R.S. et al. J Am Soc Mass Spectrom (2000) 11: 606. doi:10.1016/S1044-0305(00)00127-6

Abstract

Human glutathione S-transferase A1-1 was observed predominantly as dimeric ions (51 kDa) during electrospray mass spectrometric analysis from aqueous solution at pH 7.4, in keeping with the known dimeric structure in solution. When analyses were performed on solutions of the enzyme containing glutathione (GSH), noncovalent adducts of protein dimer and one or two ligand molecules were observed; each mass increment, which exceeded the mass of GSH alone, was provisionally interpreted to indicate concomitant association of two water molecules per bound GSH. Noncovalent adducts of ligand and protein dimer were similarly observed for oxidized glutathione and for two glutathione inhibitors, both incorporating substituted thiol structures. In these instances, the mass increments exactly matched the ligand masses, suggesting that the apparent concomitant binding of water was associated with the presence in the ligand of a free thiol group. Collisionally activated decomposition during tandem mass spectrometry analyses of noncovalent adducts incorporating protein dimer and ligands yielded initially the denuded dimer; at higher collision energies the monomer and a protein fragment were formed.

Copyright information

© American Society for Mass Spectrometry 2000