A comparative study on the interactions of human copper chaperone Cox17 with anticancer organoruthenium(II) complexes and cisplatin by mass spectrometry
Lijie Li, Wei Guo, Kui Wu, Xuelei Wu, Linhong Zhao, Yao Zhao, Qun Luo, Yuanyuan Wang, Yangzhong Liu, Qingwu Zhang, Fuyi Wang
Journal of Inorganic Biochemistry
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.
Circular dichroism, Secondary structure, Ligand binding, Inorganic chemistry, Biochemistry