Comprehensive identification of the binding sites of cisplatin in hen egg white lysozyme

Regulation of oxaliplatin and carboplatin on the assembly behavior and cytotoxicity of human islet amyloid polypeptide

Human islet amyloid polypeptide (hIAPP) is associated with the pathology of Type II diabetes (T2DM) due to its misfolding and amyloid deposition. The peptide is widely concerned as a potential drug target, and the prevention of hIAPP fibrillation is a rational therapeutic strategy for T2DM. Platinum complexes are promising anticancer agents with good biocompatibility, they can resist the aggregation of amyloid peptides, while the effects of oxaliplatin and carboplatin on hIAPP fibrillation are unknown. In the present work, we selected the two platinum drugs to reveal their inhibition and disaggregation against hIAPP fibrillation by various biophysical methods. The two complexes impeded hIAPP fibril formation and dispersed the aggregates into small oligomers and most monomers. They also reduced peptides oligomerization and promoted rat insulinoma β-cells viability. They bound to hIAPP mainly through metal coordination and hydrophobic interactions. Moreover, oxaliplatin showed better inhibition and regulation on peptides aggregation and cytotoxicity than carboplatin. This work is of important biomedical values for clinical platinum drugs against T2DM and other amyloidosis related diseases.

Noncovalent molecular interactions between antineoplastic drug gemcitabine and a carrier protein identified through spectroscopic and in silico methods

Herein we have studied the noncovalent molecular interactions between hen egg white lysozyme (HEWL) and the commonly employed antineoplastic drug gemcitabine through the cumulative implementation of spectroscopic techniques and in silico approaches. The formation of a complex between HEWL and gemcitabine was made evident by the differences between the UV-visible spectra of the protein and protein-gemcitabine complex. Fluorescence quenching of HEWL by gemcitabine was hardly detectable at room temperature, but it became prominent at higher temperatures. Very low values for the bimolecular quenching constant and the non-reciprocal dependence of quenching on temperature indicated that dynamic quenching was taking place. Analysis of experimental data indicated that the interaction was dominated by hydrophobic forces, while the results of a computational investigation suggested the concomitant contribution of hydrogen bonding. Gemcitabine binding induced modifications of the secondary structure of HEWL by slightly increasing the α-helical content of the protein. Finally, gemcitabine binding site was inferred to be located in HEWL big hydrophobic cavity.

Platinum(II) O,S Complexes Inhibit the Aggregation of Amyloid Model Systems

Platinum(II) complexes with different cinnamic acid derivatives as ligands were investigated for their ability to inhibit the aggregation process of amyloid systems derived from Aβ, Yeast Prion Protein Sup35p and the C-terminal domain of nucleophosmin 1. Thioflavin T binding assays and circular dichroism data indicate that these compounds strongly inhibit the aggregation of investigated peptides exhibiting IC₅₀ values in the micromolar range. MS analysis confirms the formation of adducts between peptides and Pt(II) complexes that are also able to reduce amyloid cytotoxicity in human SH-SY5Y neuroblastoma cells. Overall data suggests that bidentate ligands based on β-hydroxy dithiocinnamic esters can be used to develop platinum or platinoid compounds with anti-amyloid aggregation properties.

Protein metalation by metal-based drugs: X-ray crystallography and mass spectrometry studies

The combined use of X-ray crystallography and mass spectrometry represents a valuable strategy to investigate and characterize protein metalation induced by anticancer metal-based drugs. Here, we summarize a series of significant results recently obtained in our laboratories upon the examination of the structures of several adducts of proteins with representative metallodrugs (mostly containing ruthenium, gold and platinum). The general mechanisms of protein metalation that emerge from a careful comparative analysis of these structures are illustrated and their mechanistic implications are discussed. Possible directions for future work in the field are delineated.

A case of extensive protein platination: the reaction of lysozyme with a Pt(ii)–terpyridine complex

The interaction between a Pt(ii)–terpyridine cytotoxic compound and the model protein lysozyme has been investigated by X-ray crystallography and electrospray mass spectrometry under different experimental conditions. The compound shows a high reactivity with the model protein.

Mass spectrometry based strategy for studies of binding sites and structural changes of cisplatin binding to myoglobin

RATIONALE

It is of great significance to investigate the interaction of the metallodrug cisplatin (cis-[PtCl₂ (NH₃ )₂ ]) with myoglobin for understanding of the mechanism of action of cisplatin and the overexpression of myoglobin in tumor cells.

METHODS

The reactions of cisplatin and myoglobin were incubated under different conditions. A mass spectrometry (MS)-based strategy combining full proteolysis and limited proteolysis was developed for comprehensive studies of cisplatin-myoglobin interaction.

RESULTS

The binding sites of cisplatin on myoglobin were identified as Trp14, His64, His81, His113 and His116 using electrospray ionization multiple-stage tandem mass spectrometry (ESI-MSⁿ ) without liquid chromatography (LC) separation. The relative abundances of digested peptides from platinated myoglobin were obviously higher than those from native samples by limited proteolysis.

CONCLUSIONS

An alternative and simple approach was developed to successfully monitor conformational changes of myoglobin induced by cisplatin binding using an ESI-MS-based quantification method combined with limited proteolysis. Meanwhile, His64 was firstly found to coordinate to platinum, which was likely to affect hydrogen bonds with the oxygen in the heme group. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of temperature on the interaction of cisplatin with the model protein hen egg white lysozyme

The products of the reaction between cisplatin (CDDP) and the model protein hen egg white lysozyme (HEWL) at 20, 37 and 55 °C in pure water were studied by UV-Vis absorption spectroscopy, intrinsic fluorescence and circular dichroism, dynamic and electrophoretic light scattering and inductively coupled plasma mass spectrometry. X-ray structures were also solved for the adducts formed at 20 and 55 °C. Data demonstrate that high temperature facilitates the formation of CDDP-HEWL adducts, where Pt atoms bind ND1 atom of His15 or NE2 atom of His15 and NH1 atom of Arg14. Our study suggests that high human body temperature (fever) could increase the rate of drug binding to proteins thus enhancing possible toxic side effects related to CDDP administration.

Identification of protein adduction using mass spectrometry: Protein adducts as biomarkers and predictors of toxicity mechanisms

The determination of protein-xenobiotic adducts using mass spectrometry is an emerging area which allows detailed understanding of the underlying mechanisms involved in toxicity. These approaches can also be used to reveal potential biomarkers of exposure or toxic response. The following review covers studies of protein adducts resulting from exposure to a wide variety of xenobiotics including organophosphates, polycyclic aromatic hydrocarbons, acetaminophen, alkylating agents and other related compounds.

Oxaliplatin vs. cisplatin: competition experiments on their binding to lysozyme

The model protein hen egg white lysozyme was challenged with oxaliplatin and cisplatin. ESI mass spectrometry, surface plasmon resonance and thermal shift analyses demonstrate the formation of a bis-platinum adduct, though in very small amounts. Crystals of the bis-platinum adduct were obtained using two different preparations and the X-ray structures were solved at 1.85 Å and 1.95 Å resolution. Overall, the obtained data point out that, under the analyzed conditions, the two Pt drugs have similar affinities for the protein, but bind on its surface at two non-overlapping sites. In other words, these two drugs manifest a significantly different reactivity with this model protein and do not compete for the same protein binding sites.

Study of the non-covalent interactions of ginsenosides and lysozyme using electrospray ionization mass spectrometry

RATIONALE

Ginsenosides are an important class of natural products extracted from ginseng that possess various important biological activities. Studies of interactions of ginsenosides with proteins are essential for comprehensive understanding of the biological activities of ginsenosides. In this study, the interactions of ginsenosides with lysozyme were investigated by electrospray ionization mass spectrometry (ESI-MS).

METHODS

Both protopanaxadiol-type and protopanaxatriol-type ginsenosides were chosen to explore the interactions of ginsenosides towards lysozyme near the physiological conditions by direct ESI-MS, respectively. Comparative experiments were conducted to confirm the interactions were specific. In addition, the dissociation constants of ginsenoside-lysozyme complexes were determined by a ESI-MS titration strategy.

RESULTS

The results showed ginsenosides bound to lysozyme at the stoichiometries of 1:1 and 2:1. The association constants of ginsenosides to lysozyme were in the order of Re>Rd>Rf>Rg2 >Rg3 . According to their structures, the binding affinities associated with the type of aglycone and the type and the number of sugar moieties linked on the aglycone.

CONCLUSIONS

It has been demonstrated that ESI-MS is a powerful tool to probe the non-covalent interactions between lysozyme and ginsenosides. These results provide insights into the interaction of ginsenosides with lysozyme at the molecular level. The developed strategy could be applied to determine the interactions of proteins with other natural products.

Direct determination of the binding sites of cisplatin on insulin-like growth factor-1 by top-down mass spectrometry

Cisplatin has been widely used in the chemotherapy of a variety of tumors, and the interactions of cisplatin with proteins play very important roles in its side effects and drug resistance, as well as its pharmacokinetics and the biodistribution. Insulin-like growth factor-1 (IGF-1) was found to be associated with the drug resistance of cisplatin. Here, the interaction between cisplatin and IGF-1 was investigated using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. IGF-1-Pt(NH3)Cl was the main mono-adduct and the trans labilization was important to the reaction between IGF-1 and cisplatin, while another special mono-adduct IGF-1-Pt(NH3)Cl2 was observed. The rapid and sensitive top-down mass spectrometry-based approach in linear ion trap mass spectrometer has been developed to identify the binding sites of cisplatin in IGF-1 directly without tedious enzyme digestion. Three binding sites (Met59, Arg56 and Cys6) of cisplatin in IGF-1 were determined. The results not only provide a rapid and efficient way to identify the platinum binding sites in proteins, but also indicate that the binding of cisplatin could promote the fragmentation of IGF-1 and the rupture of disulfide bond.