Mass spectrometric quantification of the binding ratio of metal‐based anticancer complexes with protein thiols

Abstract

Rationale The binding ratio of metal complexes with cysteinyl thiols in proteins plays an important role in deciphering the mechanisms of action of therapeutic metal complexes, but its analysis is still a significant challenge. In this work, a quantitative mass spectrometry method is developed to determine the binding ratio of metal‐based anticancer complexes with cysteines in human copper chaperone protein Atox1. Methods A novel strategy based on a thiol‐specific stable isotopic labelling reagent was developed to determine the binding ratio of metal‐based anticancer complexes, namely cisplatin and organometallic ruthenium complex [(η6‐biphenyl)RuCl(en)]PF6 (en = ethylenediamine), with the cysteinyl residues of Atox1. Results Both cisplatin and the ruthenium complex were reactive not only to Cys15 and/or Cys18, the copper(I) binding site of Atox1, but also to Cys44. The binding ratios of the ruthenium complex with the cysteinyl residues were much higher than those of cisplatin. However, the addition of copper(I) could markedly increase the binding ratios of cysteinyl residues of Atox1 with cisplatin, but not with the ruthenium complex. Conclusions This strategy can not only precisely determine the binding ratios of metal complexes to protein thiols, but also be helpful in distinguishing thiol‐binding sites from other binding sites of metal complexes in proteins. We expect wide application of this method to the research of covalent/coordinative interactions between metal complexes and protein thiols.

Mass spectrometry insights into interactions of selenoprotein P with auranofin and cisplatin

“…The Pt/Se ratio changes showing that the dominant binding peptide may not be a selenium one. Indeed, cisplatin was reported to bind covalently to His and Met 30 and Cys 31,32 which would explain such a behaviour.…”

Investigating the exceptional adducts of alkoxides with Ru(II)–arene cations in alkyl alcohol solution using electrospray ionization mass spectrometry

“…Ru(II)–arene complexes are a class of potential metal anticancer drug molecules with high antitumor activity in vitro and low cytotoxicity 1–4 . Meanwhile, Ru(II)–arene complexes are widely used as catalysts due to their ease of preparation, 5 unique reactivity and selectivity, such as in arylation reactions, 6 catalytic reduction of esters, 7 catalytic oxidation of alcohols 8 and carbon–hydrogen bond functionalization 9 .…”