A comparative study on the interactions of human copper chaperone Cox17 with anticancer organoruthenium(II) complexes and cisplatin by mass spectrometry

• Study on interactions of anticancer Ru arene complexes with human copper chaperone Cox17.
• Ru arene complexes are much less reactive than cisplatin to Cox17.
• Both Ru and Pt can bind to Cys27 which is the Cu(I) binding site on Cox17.
• Cox17 may not be involved in the action of anticancer Ru arene complexes.
• First report about interactions of Ru arene complexes with Cox17.

Herein we report investigation of the interactions between anticancer organoruthenium complexes, [(η6-arene)Ru(en)(Cl)]PF6 (en = ethylenediamine, arene = p-cymene (1) or biphenyl (2)), and the human copper chaperone protein Cox17 by mass spectrometry with cisplatin as a reference. The electrospray ionization mass spectrometry (ESI-MS) results indicate much weaker binding of the ruthenium complexes than that of cisplatin to apo-Cox172s-s, the functional state of Cox17. Up to tetra-platinated Cox17 adducts were identified while only mono-ruthenated and a little amount of di-ruthenated Cox17 adducts were detected even for the reactions with 10-fold excess of the Ru complexes. However, ESI-MS analysis coupled with liquid chromatography of tryptic digests of metalated proteins identified only three platination sites as Met4, Cys27 and His47 residues, possibly due to the lower abundance or facile dissociation of Pt bindings at other sites. Complexes 1 and 2 were found to bind to the same three residues with Met4 as the major site. Inductively coupled plasma mass spectrometry results revealed that ~ 7 mol Pt binding to 1 mol apo-Cox172s-s molecules, compared to only 0.17 (1) and 0.10 (2) mol Ru to 1 mol apo-Cox172s-s. This is in line with the circular dichroism results that much larger unfolding extent of α-helix of apo-Cox172s-s was observed upon cisplatin binding than that upon organoruthenium bindings. These results collectively indicate that Cox17 might not participate in the action of these anticancer organoruthenium complexes, and further verify the distinct anticancer mechanism of the organoruthenium(II) complexes from cisplatin.

The interactions of anticancer organoruthenium(II) complexes with human copper chaperone Cox17 were investigated by mass spectrometry compared with cisplatin, revealing that they share the same binding sites as cisplatin but are much less reactive towards Cox17. This implies that Cox17 may not be involved in action of organoruthenium(II) complexes.Figure optionsDownload as PowerPoint slide