The conformational space sampled by the two-domain protein calmodulin has been explored by an approach based on four sets of NMR observables obtained on Tb 3+ - and Tm 3+ -substituted proteins. The observables are the pseudocontact shifts and residual dipolar couplings of the C-terminal domain when lanthanide substitution is at the N-terminal domain. Each set of observables provides independent information on the conformations experienced by the molecule. It is found that not all sterically allowed conformations are equally populated. Taking the N-terminal domain as the reference, the C-terminal domain preferentially resides in a region of space inscribed in a wide elliptical cone. The axis of the cone is tilted by ≈30° with respect to the direction of the N-terminal part of the interdomain helix, which is known to have a flexible central part in solution. The C-terminal domain also undergoes rotation about the axis defined by the C-terminal part of the interdomain helix. Neither the extended helix conformation initially observed in the solid state for free calcium calmodulin nor the closed conformation(s) adopted by calcium calmodulin either alone or in its adduct(s) with target peptide(s) is among the most preferred ones. These findings are unique, both in terms of structural information obtained on a biomolecule that samples multiple conformations and in terms of the approach developed to achieve the results. The same approach is in principle applicable to other multidomain proteins, as well as to multiple interaction modes between two macromolecular partners.

Cap43 protein has been tested for metal binding domains. The protein, specifically induced by nickel compounds in cultured human cells, had a new mono-histidinic motif consisting of 10 amino acids repeated three times in the C-terminus. The 20-Ac-TRSRSHTSEG-TRSRSHTSEG (Thr(341)-Arg-Ser-Arg-Ser-His(346)-Thr-Ser-Glu-Gly-Thr-Arg-Ser-Arg-Ser-His(356)-Thr-Ser-Glu-Gly(360) - peptide 1) and the 30-Ac-TRSRSHTSEG-TRSRSHTSEG-TRSRSHTSEG (Thr(341)-Arg-Ser-Arg-Ser-His(346)-Thr-Ser-Glu-Gly-Thr-Arg-Ser-Arg-Ser-His(356)-Thr-Ser-Glu-Gly-Thr-Arg-Ser-Arg-Ser-His(366)-Thr-Ser-Glu-Gly(370) - peptide 2) amino acids sequence has been analyzed as a site for Ni(II) binding. A combined pH-metric and spectroscopic (UV-visible, CD, NMR) studies of Ni(II) binding to both fragments were performed. The 20-amino acid peptide can bind one and two metal ions while the 30-amino acid fragment one, two and three metal ions. At physiological pH, depending on the metal to ligand molar ratio, peptide 1 forms the Ni(2)L species while peptide 2 the NiL, Ni(2)L and Ni(3)L complexes where each metal ion is coordinated to the imidazole nitrogen atom of the histidine residue of the 10-amino acid fragment. Octahedral complexes at pH 8-9 and planar 4N complexes with (N(Im), 3N(-)) bonding mode at pH above 9, are formed. This work supports the existence of an interesting binding site at the COOH-terminal domain of the Cap43 protein.

Copper(II) complexes of carvedilol molecule, (CARVH): 1-[carbazolyl-(4)-oxyl]-3-[(2-methoxyphenoxyethyl)-amino]-2-propanol, were synthesized and characterized with respect to their structural and spectroscopic properties. The crystal structure of [Cu(Carv)Cl(MeOH)](2).4MeOH complex revealed that the molecule chelates two Cu(II) ions via the N and O atoms belonging to the amino and propanol moiety, respectively. The coordination behaviour of carvedilol studied by 1H nuclear magnetic resonance (NMR, 1-D and 2-D-COSY) spectroscopy in dimethyl sulfoxide solution at room temperature, allowed us to obtain structural information and to identify the donor atoms involved in the coordination process in solution.

PrefaceOpen AccessThird International Meeting on the Molecular Mechanisms of Metal Toxicity and Carcinogenicity M Costa M Costa Search for more papers by this author Published:1 October 2002https://doi.org/10.1289/ehp.110-1241225AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit "Third International Meeting on the Molecular Mechanisms of Metal Toxicity and Carcinogenicity." Environmental Health Perspectives, 110(suppl 5), p. 687FiguresReferencesRelatedDetails Vol. 110, No. suppl 5 October 2002Metrics About Article Metrics Publication History Originally published1 October 2002Published in print1 October 2002 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

Nickel has been shown to be an essential trace element involved in the metabolism of several species of bacteria, archea, and plants. In these organisms, nickel is involved in enzymes that catalyze both non-redox (e.g., urease, glyoxalase I) and redox (e.g., hydrogenase, carbon monoxide dehydrogenase, superoxide dismutase) reactions, and proteins involved in the transport, storage, metallocenter assembly, and regulation of nickel concentration have evolved. Studies of structure/function relationships in nickel biochemistry reveal that cysteine ligands are used to stabilize the Ni(III/II) redox couple. Certain nickel compounds have also been shown to be potent human carcinogens. A likely target for carcinogenic nickel is nuclear histone proteins. Here we present X-ray absorption spectroscopic studies of a model Ni peptide designed to help characterize the structure of the nickel complexes formed with histones and place them in the context of nickel structure/function relationships, to gain insights into the molecular mechanism of nickel carcinogenesis.

We have analyzed, for Ni(II) and Cu(II) binding, the sequence of the N-terminal tail of the histone H4, the 22-amino acid peptide Ac-SGRGKGGKGLGKGGAKRHRKVL-Am and, in addition, the 7- and 11-amino acid peptides Ac-AK(Ac)RHRK(Ac)V-Am, Ac-GK(Ac)GGAK(Ac)RHRK(Ac)V-Am where all side chains of lysines were blocked by acetylation. Potentiometric and spectroscopic studies (UV-Vis, CD, EPR, NMR) showed that histidine 18 acted as an anchoring binding site for metal ions in all the peptides investigated. The stability constants of the 3N and 4N complexes are higher than those obtained for simple peptides with glycine instead of arginine and lysine residues in the metal binding site. The coordination was not significantly affected by the acetylation of lysines. The behavior of the “tail” suggested a possible bent structure with organized side-chain orientation promoted by Ni(II).

The tetradecapeptide containing the 10 aminoacid repeated sequence on the C-terminus of the Ni(II)-induced Cap43 protein, was analyzed for Ni(II) and Cu(II) binding. A combined pH-metric and spectroscopic UV–VIS, EPR, CD and NMR study of Ni(II) and Cu(II) binding to the blocked CH3CO-Thr-Arg-Ser-Arg-Ser-His-Thr-Ser-Glu-Gly-Thr-Arg-Ser-Arg-NH2 (Ac-TRSRSHTSEGTRSR-Am) peptide, modeling a part of the C-terminal sequence of the Cap43 protein, revealed the formation of octahedral complexes involving imidazole nitrogen of histidine, at pH 5.5 and pH 7 for Cu(II) and Ni(II), respectively; a major square planar 4N–Ni(II) complex (about 100% at pH 9, log K*=−28.16) involving imidazole nitrogen of histidine and three deprotonated amide nitrogens of the backbone of the peptide was revealed; a 3N–Cu(II) complex (maximum about 70% at pH 7, log K*=−13.91) and a series of 4N–Cu(II) complexes starting at pH 5.5 (maximum about 90% at pH 8.7, log K*=−21.39 for CuH−3L), were revealed. This work supports the existence of a metal binding site at the COOH-terminal part of the Cap43 peptide.

Chromatin proteins are believed to represent reactive sites for nickel binding. The unique structure of the N-terminal tail of histone H4 contains sites for post-translational modification close to a histidine residue capable of anchoring binding sites for metal ions. We have analyzed as a minimal model for the H4 tail, the blocked peptide CH3CO-AKRHRK-CONH2 for nickel and copper binding. Ultraviolet–visible, circular dichroism, electron paramagnetic resonance and nuclear magnetic resonance spectroscopic analysis showed that histidine acts as an anchoring metal binding site. A 1N complex is formed between pH=5–7 and 4–6 for Ni(II) and Cu(II), respectively, while at a higher pH a series of 4N complexes are formed. Above pH 8, the 2N high-spin octahedral resulted in a 4N low-spin planar Ni(II) complex. The stability constants of the Cu(II) (3N, 4N) and Ni(II) (4N) complexes with the peptide model of the H4 were distinctly higher than those for a similar blocked peptide with a histidine in the fourth position. Significant shifts in the αproton region in the 1H NMR spectrum of the 4N Ni-complex showed that the conformation of the peptide had been dramatically affected following Ni(II) complexation.

Annals of the New York Academy of SciencesVolume 879, Issue 1 p. 288-291 Vanadium Uptake by Yeasts MARIA ANTONIETTA ZORODDU, Corresponding Author MARIA ANTONIETTA ZORODDU Dipartimento di Chimica, Via Vienna 2, 07100 Sassari, Italy Address for correspondence: 079-229559 (fax); zoroddu@ssmain.uniss.it (e-mail)Search for more papers by this author MARIA ANTONIETTA ZORODDU, Corresponding Author MARIA ANTONIETTA ZORODDU Dipartimento di Chimica, Via Vienna 2, 07100 Sassari, Italy Address for correspondence: 079-229559 (fax); zoroddu@ssmain.uniss.it (e-mail)Search for more papers by this author First published: 06 February 2006 https://doi.org/10.1111/j.1749-6632.1999.tb10434.xCitations: 1Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume879, Issue1TEMPOS IN SCIENCE AND NATURE: STRUCTURES, RELATIONS, AND COMPLEXITYJune 1999Pages 288-291 RelatedInformation

Saccharomyces cerevisiae cells stored oxovanadium (IV) ions in a dimeric form. In the late stationary phase Saccharomyces cerevisiae cells grown in rich medium containing concentrations of oxovanadium (V), orthovanadate from 12 to 18 mM, causing growth stasis, a dimeric oxovanadium (IV) species was identified by EPR spectroscopy. The EPR spectrum exhibited at 110 K the low-field forbidden ΔMs=±2 transition at g around 4 and the half-field ΔMs=±1 15-lines feature at g around 2 out of the presence of a triplet state by the coupling of the oxovanadium (IV) ions in a dimeric form. Hyperfine splitting of 75.2×10−4 cm−1 and an interionic distance of about 4.4 Å was calculated. The dimeric species was localized in the cellular cytoplasmic space.

Monoanionic complexes of chromium(III) like [Cr(sq)(2)(cat)](-), where the ligands are anionic radicals such as 1,2-semiquinones and catecholates unsubstituted and 3,5-di-tert-butyl-substituted were detected after interaction of chromate anion (Cr(VI), natural isotope, I = 0 or Cr-53-enriched isotope, I = 3/2) with 1,2-catechol or 3,5-di-tert-butyl-1,2-catechol in methanolic, ethanolic, or aqueous solution under both anaerobic and aerobic conditions.The very low [g] values (g = 1.972) obtained in methanol for both complexes, and the very strong metal hyperfine coupling, A53(Cr) = 25.71 G and A53(Cr) = 25.17 G for the complex with the ligands 1,2-catechol and 3,5-di-tert-butyl-1,2-catechol, respectively, suggest a ground state localized on the metal ion.The unpaired electron could be localized in a molecular orbital with a large metal character. The isotropic spectra obtained at room temperature as well as at low temperature suggest an essential octahedral arrangement around the chromium ion. The H-1 ENDOR spectra confirm the octahedral geometry of the complexes.