Interactions of carboplatin and oxaliplatin with proteins: Insights from X-ray structures and mass spectrometry studies of their ribonuclease A adducts

Abstract

Oxaliplatin and carboplatin are two platinum(II) drugs in widespread clinical use for the treatment of various types of cancers; yet, structural information on their interactions with proteins is scarce. Here, the X-ray structures of the adducts formed upon reaction of carboplatin and oxaliplatin with bovine pancreatic ribonuclease (RNase A) are reported and compared with results obtained for the structure of the RNase A-cisplatin adduct derived from isomorphous crystals, under the same experimental conditions. Additional details on the binding mode of these metallodrugs toward RNase A are provided by electrospray ionization mass spectrometry (ESI MS) measurements, thus offering insight on the occurring metal-protein interactions. Notably, while carboplatin and cisplatin mainly bind the side chain of Met29, oxaliplatin also binds the side chains of Asp14, of catalytically important His119 and, to a lesser extent, of His105. On the basis of the available data, a likely mechanism for oxaliplatin hydrolysis and binding to the protein is proposed. These results are potentially useful for a better understanding of the biological chemistry, toxicity and side effects of this important class of antitumor agents.

X-ray Structure of the Carboplatin-Loaded Apo-Ferritin Nanocage

“…41,42 It is also interesting to note that CBDCA binding to His side chains has already been observed in the crystal structure of the adduct that the drug forms with RNase A. 43 His side chains have been also found frequently in the adduct that cisplatin and other Pt-based drugs form with proteins. 44−48 Although Ft is believed to be a very good delivery system for antitumor metallodrugs, 27−32 structural features of drug-loaded Ft systems were rarely investigated.…”

“…The inability to observe the Pt ligand of carboplatin upon interaction with proteins seems a general feature since it has been a challenge reported by Tanley et al in their extensive survey of crystallization conditions of lysozyme−carboplatin adducts 41,42 and by Messori et al in the X-ray structure of the adduct formed in the reaction between carboplatin and bovine pancreatic ribonuclease (RNase A). 43 Close to one of the two His49 conformers, a Pt atom interacts also with the side chain of Glu45 ( Figure 1C). Interestingly, the electron density close to the His132 side chain and close to the other conformation of the His49 side chain is reminiscent of that observed in the X-ray structure of the adduct formed in the reaction between hen egg white lysozyme and CBDCA.…”

Protein Metalation by Anticancer Metallodrugs: A Joint ESI MS and XRD Investigative Strategy

“…Notably,t he information on Pt-drugs/RNase Aa dducts derived from ESI MS experiments was complemented with independenti nformation comingf rom crystallographic studies on the same systems, [13] the latter typicallyb eing more laborious and time consuming. Despite the big differences in the respective experimental conditions, highly consistentr esults were commonlyo btained through application of these two meth-ods.…”

“…Despite the big differences in the respective experimental conditions, highly consistentr esults were commonlyo btained through application of these two meth-ods. Indeed,t he crystal structures of RNase Aa dducts of the three clinically established Pt compounds were solved at resolutions ranging between 1.85 and 2.27 [13] and detailso ft he Pt environment could be clarified in most cases (see for example Figure 2d-f). Inspection of electron density maps in these structures reveals that the number and the nature of protein bound fragments often coincide with those suggested by ESI MS;M et and His side chains being the main Pt anchoring sites.…”

Top-down mass spectrometry reveals multiple interactions of an acetylsalicylic acid bearing Zeise’s salt derivative with peptides

“…While protein binding may serve as transport mechanism, the high reactivity of Pt II complexes with enzymes is likely a primary cause for the large number of dose-limiting side effects of Pt II -based chemotherapy [36]. Sulfur-containing Met and Cys as well as the nitrogen donor His are generally accepted binding partners for cisplatin and other Pt II compounds [37][38][39][40][41][42][43]. While thiols and thioethers rapidly displace chlorido ligands on cisplatin directly, reactions with amines require a rate-determining aquation step first [44].…”