Probing the HIV-1 NCp7 Nucleocapsid Protein with Site-Specific Gold(I)–Phosphine Complexes

Abstract

In this work, we examined a series of thiophilic Au(I) compounds based on [Au(L)(PR)] (L = Cl, 4-dimethylaminopyridine (dmap); R= ethyl (Et), cyclohexyl (Cy)) for chemoselective auration of the C-terminal HIV nucleocapsid protein NCp7 F2 and the "full" HIV NCp7 (NC, zinc finger (ZnF)) as probes of nucleocapsid topography. The choice of phosphine allowed electronic and steric effects to be considered. The use of the heterocycle "leaving group" allowed us to study the effect of possible π-stacking with the essential tryptophan residue of NC on the reactivity and selectivity, mimicking the naturally occurring interaction between the zinc finger and nucleic acids. We also examined for comparison the "standard" gold-phosphine compound auranofin, which contains an S-bound glucose coordinated to the {Au(PEt)} moiety. Both the nature of the phosphine and the nature of L affect the reactivity with the C-terminal NCp7 F2 and the "full" NC. P NMR spectroscopy showed the formation of long-lived {Au(PR)}-ZnF species in all cases, but in the case of NCp7 F2, a selective interaction in the presence of the dmap ligand was observed. In the case of auranofin, an unusual Au-His (rather than Au-Cys) coordination was indicated on NC. The overall results suggest that it is useful to consider three aspects of zinc finger structure in considering the profile of chemical reactivity: (i) the zinc-bound cysteines as primary nucleophiles; (ii) the zinc-bound histidine as a "spectator" ligand; and (iii) ancillary groups not bound to Zn but essential for ZnF function such as the essential tryptophan in NCp7 F2 and NC. Modification of fully functional NC zinc finger by the CyP-containing species confirmed the inhibition of the NC-SL2 DNA interaction, as evaluated by fluorescence polarization.

Selective targeting of PARP-1 zinc finger recognition domains with Au(iii) organometallics

“…2,12,[15][16][17] Recently, Farrell et al investigated the binding of coordination Au(III)/Au(I) complexes to the ZF of the HIV-nucleocapsid protein (NCp7) by high resolution and traveling-wave ion mobility mass spectrometry, respectively. [17][18][19] Despite these encouraging results, doubts remain on the selectivity of anticancer Au(III) compounds for discriminating between CCHC over CCHH or CCCC coordination motifs, as such compounds were shown to interact with CCHH and CCCC zinc fingers alike, when incubated individually. 2,15 Sampling the metallodrug binding selectivity for intact protein domains under "competitive" conditions -such as those encountered in a cellular context -represents a considerable experimental challenge, 20 which is mainly caused by the difficulty of separating the intact reaction products, by potential ligand scrambling reactions and by redox reactivity during lengthy work-up and analysis.…”

Bioinorganic applications of gold and platinum coordination compounds: a brief historical overview and recent advances in 2017

“…A series of thiophilic Au(I)-phosphine compounds (3-7) was evaluated by Paiva et al [3] for chemoselective auration of the C-terminal HIV nucleocapsid protein NCp7 zinc finger 2 (F2) and the full-length HIV NCp7 (NC), as probes of nucleocapsid topography. The nature of the phosphine and the co-ligand affect the reactivity with the C-terminal NCp7 F2 and the full-length NC.…”

“…Curiously enough, the first uses of gold(I) compounds in treatment of rheumatoid arthritis were based on the idea that such illness was caused by a bacterial infection, which was shown to be incorrect. [1] Mirroring the historical application of gold and goldcontaining compounds for the treatment of such a wide variety of diseases, the 2016-2017 period has introduced gold-based metallodrugs for applications including the molecular understanding of the mechanisms of interaction with protein targets [3][4][5][6][7][8] and development of new therapeutic agents for HIV, cancer, [9,10] bacterial infections [11] as well as parasitic infections. [12] Platinum compounds, on the other hand, were intensively studied since the middle 1960's after the serendipitous discovery of the antitumor activity of cisplatin by Rosenberg.…”

Gold‐Catalyzed C–S Aryl‐Group Transfer in Zinc Finger Proteins

“…This latter observation confirms the conceptual utility of gold complexes as thiophilic probes of the ZnF structure. [18] For 2-4 and the C-terminal ZnF2, only Au n Fs pecies are observed (see Figures S8-S10). All previously reported cysteinem ethylations in zinc finger biology has occurred in ZnCys 4 and ZnCys 3 His coordination spheres.…”

“…In this case,e arly time points show an umber of species containing both the {Au(bnpy)} and Zn ions.A long with the emergence of the C À S{ (bnpy)-oxiF} transfer product, as pecies corresponding to {(Au(bnpy)) 3 -F} 3+ also appears over time,i mplying simultaneous auration of all three cysteines of the peptide by the {Au(bnpy)} moiety ( Figure 3B;s ee Figure S7). [18] For 2-4 and the C-terminal ZnF2, only Au n Fs pecies are observed (see Figures S8-S10). [18] For 2-4 and the C-terminal ZnF2, only Au n Fs pecies are observed (see Figures S8-S10).…”