Reactivity of Cys4 zinc finger domains with gold(III) complexes: insights into the formation of "gold fingers".

Gold(I) complexes such as auranofin or aurothiomalate have been used as therapeutic agents for the treatment of rheumatoid arthritis for several decades. Several gold(I) and gold(III) complexes have also shown in vitro anticancer properties against human cancer cell lines, including cell lines resistant to cisplatin. Because of the thiophilicity of gold, cysteine-containing proteins appear as likely targets for gold complexes. Among them, zinc finger proteins have attracted attention and, recently, gold(I) and gold(III) complexes have been shown to inhibit poly(adenosine diphosphate ribose)polymerase-1 (PARP-1), which is an essential protein involved in DNA repair and in cancer resistance to chemotherapies. In this Article, we characterize the reactivity of the gold(III) complex [Au(III)(terpy)Cl]Cl2 (Auterpy) with a model of Zn(Cys)4 "zinc ribbon" zinc finger by a combination of absorption spectroscopy, circular dichroism, mass spectrometry, high-performance liquid chromatography analysis, and X-ray absorption spectroscopy. We show that the Zn(Cys)4 site of Zn·LZR is rapidly oxidized by Auterpy to form a disulfide bond. The Zn(2+) ion is released, and the two remaining cysteines coordinate the Au(+) ion that is produced during the redox reaction. Subsequent oxidation of these cysteines can take place in conditions of excess gold(III) complex. In the presence of excess free thiols mimicking the presence of glutathione in cells, mixing of the zinc finger model and gold(III) complex yields a different product: complex (Au(I))2·LZR with two Au(+) ions bound to cysteines is formed. Thus, on the basis of detailed speciation and kinetic measurements, we demonstrate herein that the destruction of Zn(Cys)4 zinc fingers by gold(III) complexes to achieve the formation of "gold fingers" is worth consideration, either directly or mediated by reducing agents.

On the design of zinc-finger models with cyclic peptides bearing a linear tail.

Cyclic peptides with a linear tail (CPLT) have been successfully used to model two zinc fingers (ZFs) adopting the treble-clef- and loosened zinc-ribbon folds. In this article, we examine the factors that may influence the design of such ZF models: mutations in the sequence, size of the cycle, and size of the tail. For this purpose, several peptides derived from the CPLT-based models of the treble-clef- and loosened zinc-ribbon ZF were synthesized and studied. CPLT-based models appear to be robust toward mutations, accommodate various cycle sizes, and are sensible to the size of the linking region of the tail located between the cycle and the coordinating amino acids. Based on these criteria, we describe the design of a new CPLT-based model for the zinc-ribbon ZFs, LZR , and compare it to a linear analogue, LZR(lin) . The model complex Zn⋅LZR is able to fold correctly around the metal ion contrary to Zn⋅LZR(lin) , suggesting that CPLT-based models are more likely to yield structurally meaningful models of ZF sites than linear peptide models. Finally, we draw some rules that could allow the design of new CPLT-based metallopeptides with a controlled fold.

Peptide-based FeS4 complexes: the zinc ribbon fold is unsurpassed to stabilize both the FeII and FeIII states.

Whereas Zn(Cys)4 zinc fingers exist with different protein folds, only the zinc ribbon fold is found in rubredoxin Fe(Cys)4 sites. To assess the significance of this observation, we have investigated the binding and stability of Fe(2+) and Fe(3+) ions by a set of four peptides designed to model Zn(Cys)4 zinc fingers with various folds, i.e. zinc ribbon, treble clef and a loosened zinc ribbon fold. All peptides were shown by means of UV-Vis and CD spectroscopies to form stable 1 : 1 Fe(II)/peptide complexes with binding constants higher than 10(7) M(-1) at pH 7. Their oxidation into Fe(III) complexes and the stability of the latter were compared. The UV-Vis absorption and CD spectroscopic properties of the Fe(II) and Fe(III) complexes were analysed with respect to the structures of the zinc analogues in order to get insight into the local arrangement of the Fe(Cys)4 core around the metal ion. The chemical stability of these complexes was rationalized according to the shielding from the solvent provided by the various peptide folds to the FeS4 core. In addition, we showed that whereas UV-visible spectra inform only on the FeS4, the information derived from the corresponding CD spectra extend to the Cß orientation and the peptide fold. The results presented here demonstrate that while the zinc ribbon fold is not strictly required to obtain a Fe(Cys)4 site, it affords a drastically superior protection of the site toward external redox agents. This finding brings new clues to engineer stable and redox-active Fe(Cys)4 sites in de novo proteins.

Shortening of the QT interval is observed soon after sleeve gastrectomy in morbidly obese patients.

BACKGROUND: Morbidly obese patients have an increased risk of sudden cardiac death. It is well known that obesity prolongs the QT interval, which in turn may cause ventricular arrhythmia and sudden cardiac death. The objective of this study was to establish whether sleeve gastrectomy shortens the QT interval. METHODS: Twenty-eight consecutive patients underwent sleeve gastrectomy at our institution between September 2010 and March 2011 and were included in the study. The indications for bariatric surgery were in accordance with French national guidelines. For each patient, an electrocardiogram was recorded before and then 3 months after surgery. The corrected QT (QTc) was determined independently by two physicians. RESULTS: The mean body mass index was 45.27 ± 6.09 kg/m(2) before surgery and 38.32 ± 5.19 kg/m(2) 3 months after surgery. The mean weight loss over this period was 20.71 ± 7.57 kg. The QTc interval was 427 ± 18.6 ms (415.7 ± 12.06 in men and 428.4 ± 18.96 in women) prior to surgery and was significantly lower 3 months after surgery (398.6 ± 15.5 ms overall, 391.3 ± 7.63 in men, and 399.6 ± 16.02 in women). The QTc interval decreased in all individual patients (by an average of 28.5 ± 15.6 ms overall, 24.3 ± 8.38 in men, and 29 ± 16.23 in women). Weight loss and decreased QTc interval were not significantly correlated (p = 0.88). CONCLUSION: Sleeve gastrectomy in morbidly obese patients was associated with a significantly lower QTc interval 3 months after surgery. These findings imply that bariatric surgery might reduce the risk of sudden cardiac death in this patient population.

A cyclic peptide-based redox-active model of rubredoxin.

A model of rubredoxin based on a cyclic peptide with a linear tail is presented. This model reproduces almost perfectly the fold, the spectroscopic characterizations and the redox activity of rubredoxins.