skip to main content

Explore Research Products in the NSF-PAR

  • NSF Public Access
  • Search Results
  • Comparison of the pH‐dependent formation of His and Cys heptapeptide complexes of nickel(II), copper(II), and zinc(II) as determined by ion mobility‐mass spectrometry
Title: Comparison of the pH‐dependent formation of His and Cys heptapeptide complexes of nickel(II), copper(II), and zinc(II) as determined by ion mobility‐mass spectrometry
Abstract

The analog methanobactin (amb) peptide with the sequence ac‐His1‐Cys2‐Gly3‐Pro4‐Tyr5‐His6‐Cys7(amb5A) will bind the metal ions of zinc, nickel, and copper. To further understand how amb5Abinds these metals, we have undertaken a series of studies of structurally related heptapeptides where one or two of the potential His or Cys binding sites have been replaced by Gly, or the C‐terminus has been blocked by amidation. The studies were designed to compare how these metals bind to these sequences in different pH solutions of pH 4.2 to 10 and utilized native electrospray ionization (ESI) with ion mobility‐mass spectrometry (IM‐MS) which allows for the quantitative analysis of the charged species produced during the reactions. The native ESI conditions were chosen to conserve as much of the solution‐phase behavior of the amb peptides as possible and an analysis of how the IM‐MS results compare with the expected solution‐phase behavior is discussed. The oligopeptides studied here have applications for tag‐based protein purification methods, as therapeutics for diseases caused by elevated metal ion levels or as inhibitors for metal‐protein enzymes such as matrix metalloproteinases.

  more » « less
Award ID(s):
1764436
NSF-PAR ID:
10457677
Author(s) / Creator(s):
 ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Journal of Mass Spectrometry
Volume:
55
Issue:
3
ISSN:
1076-5174
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ( , Physical Chemistry Chemical Physics)
    null (Ed.)
    Chemical dynamics simulations are performed to study the collision induced gas phase unimolecular fragmentation of a model peptide with the sequence acetyl-His 1 -Cys 2 -Gly 3 -Pro 4 -Tyr 5 -His 6 -Cys 7 (analogue methanobactin peptide-5, amb 5 ) and in particular to explore the role of zinc binding in reactivity. Fragmentation pathways, their mechanisms, and collision energy transfer are discussed. The probability distributions of the pathways are compared with the results of the experimental IM-MS, MS/MS spectrum and previous thermal simulations. Collisional activation gives both statistical and non-statistical fragmentation pathways with non-statistical shattering mechanisms accounting for a relevant percentage of reactive trajectories, becoming dominant at higher energies. The tetra-coordination of zinc changes qualitative and quantitative fragmentation, in particular the shattering. The collision energy threshold for the shattering mechanism was found to be 118.9 kcal mol −1 which is substantially higher than the statistical Arrhenius activation barrier of 35.8 kcal mol −1 identified previously during thermal simulations. This difference can be attributed to the tetra-coordinated zinc complex that hinders the availability of the sidechains to undergo direct collision with the Ar projectile. 
    more » « less
  2. ; ; ( , European Journal of Inorganic Chemistry)
    Abstract

    ZF proteins are ubiquitous eukaryotic proteins that play important roles in gene regulation. ZFs contain small domains made up of a combination of four cysteine and histidine residues and are classified on the basis of the identity of these residues and their spacing. One emerging class of ZFs are the Cys3His (or CCCH) class of ZFs. These ZFs play key roles in regulating RNA. In this minireview, an overview of the CCCH class of ZFs, with a focus on tristetraprolin (TTP), is provided. TTP regulates inflammation by controlling cytokine mRNAs, and there is an interest in modulating TTP activity to control inflammation. Two methods to control TTP activity are to target with exogenous metals (a “metals in medicine” approach) or to target with endogenous signaling molecules. Work that has been done to target TTP with Fe, Cu, Cd, and Au as well as with H2S is reviewed. This includes attention to new methods that have been developed to monitor metal exchange with the spectroscopically silent ZnIIincluding native electro‐spray ionization mass spectrometry (ESI‐MS), spin‐filter inductively coupled plasma mass spectrometry (ICP‐MS), and cryo‐electro‐spray mass spectrometry (CSI‐MS); along with fluorescence anisotropy (FA) to follow RNA binding.

     
    more » « less
  3. ; ; ; ; ( , Bioinorganic Chemistry and Applications)
    Osella, Domenico (Ed.)
    Tetrapeptides containing a Cys-Gly-Cys motif and a propensity to adopt a reverse-turn structure were synthesized to evaluate how O-, N-, H-, and aromatic π donor groups might contribute to mercury(II) complex formation. Tetrapeptides Xaa-Cys-Gly-Cys, where Xaa is glycine, glutamate, histidine, or tryptophan, were prepared and reacted with mercury(II) chloride. Their complexation with mercury(II) was studied by spectroscopic methods and computational modeling. UV-vis studies confirmed that mercury(II) binds to the cysteinyl thiolates as indicated by characteristic ligand-to-metal-charge-transfer transitions for bisthiolated S-Hg-S complexes, which correspond to 1 : 1 mercury-peptide complex formation. ESI-MS data also showed dominant 1 : 1 mercury-peptide adducts that are consistent with double deprotonations from the cysteinyl thiols to form thiolates. These complexes exhibited a strong positive circular dichroism band at 210 nm and a negative band at 193 nm, indicating that these peptides adopted a β-turn structure after binding mercury(II). Theoretical studies confirmed that optimized 1 : 1 mercury-peptide complexes adopt β-turns stabilized by intramolecular hydrogen bonds. These optimized structures also illustrate how specific N-terminal side-chain donor groups can assume intramolecular interactions and contribute to complex stability. Fluorescence quenching results provided supporting data that the indole donor group could interact with the coordinated mercury. The results from this study indicate that N-terminal side-chain residues containing carboxylate, imidazole, or indole groups can participate in stabilizing dithiolated mercury(II) complexes. These structural insights on peripheral mercury-peptide interactions provide additional understanding of the chemistry of mercury(II) with side-chain donor groups in peptides. 
    more » « less
  4. ; ; ; ; ; ( , Rapid Communications in Mass Spectrometry)
    Rationale

    Coordinatively driven self‐assembly of transition metal ions and bidentate ligands gives rise to organometallic complexes that usually contain superimposed isobars, isomers, and conformers. In this study, the double dispersion ability of ion mobility mass spectrometry (IM‐MS) was used to provide a comprehensive structural characterization of the self‐assembled supramolecular complexes by their mass and charge, revealed by the MS event, and their shape and collision cross‐section (Ω), revealed by the IM event.

     Methods

    Self‐assembled complexes were synthesized by reacting a bis(terpyridine) ligand exhibiting a 60odihedral angle between the two ligating terpyridine sites (T) with divalent Zn, Ni, Cd, or Fe. The products were isolated as (Metal2+[T])n(PF6)2nsalts and analyzed using IM‐MS after electrospray ionization (ESI) which produced several charge states from eachn‐mer, depending on the number of PF6ˉ anions lost upon ESI. Experimental Ω data, derived using IM‐MS, and computational Ω predictions were used to elucidate the size and architecture of the complexes.

     Results

    Only macrocyclic dimers, trimers, and tetramers were observed with Cd2+, whereas Zn2+formed the same plus hexameric complexes. These two metals led to the simplest product distributions and no linear isomers. In sharp contrast, Ni2+and Fe2+formed all possible ring sizes from dimer to hexamer as well as various linear isomers. The experimental and theoretical Ω data indicated rather planar macrocyclic geometries for the dimers and trimers, twisted 3D architectures for the larger rings, and substantially larger sizes with spiral conformation for the linear congeners. Adding PF6ˉ to the same complex was found to mainly cause size contraction due to new stabilizing anion–cation interactions.

     Conclusions

    Complete structural identification could be accomplished using ESI‐IM‐MS. Our results affirm that self‐assembly with Cd2+and Zn2+proceeds through reversible equilibria that generate the thermodynamically most stable structures, encompassing exclusively macrocyclic architectures that readily accommodate the 60oligand used. In contrast, complexation with Ni2+and Fe2+, which form stronger coordinative bonds, proceeds through kinetic control, leading to more complex mixtures and kinetically trapped less stable architectures, such as macrocyclic pentamers and linear isomers.

     
    more » « less
  5. ; ; ; ; ( , Metallomics)
    The toxicity of lead, one of the most ubiquitous toxic metals, is well known. Some of its pathological effects are related to its preference for the sulfhydryl groups of proteins. Metallothioneins (MT) are a particular family of metalloproteins characterized by their high Cys content that, among other functions, are linked to the detoxification of heavy metals. In mammals, 4 MT isoforms have been found. The MT3 isoform, also called “neuronal growth inhibitory factor”, is mainly synthesized in the brain and contains several structural differences that may contribute to important functional differences between it and other MT isoforms. The abilities of recombinant MT3 and its individual αMT3 and βMT3 fragments to bind Pb( ii ) have been investigated here, under different pH conditions, by means of spectroscopy, mass spectrometry and isothermal titration calorimetry. The results obtained show that the binding of Pb( ii ) to the intact MT3 protein is relatively unaffected by pH, while the individual domains interact with Pb( ii ) in a pH-sensitive manner. The mass spectrometry data reveal the evolution with time of the initially formed Pb-MT complexes. In the case of the full length protein, Pb( ii ) remains bound for a long period of time. With the isolated fragments, the lead is eventually released. The Pb-species formed depend on the amount of Pb( ii ) present in solution. The thermodynamic data recorded, as measured by ITC, for the replacement of Zn( ii ) by Pb( ii ) in reactions with Zn-MT3, Zn-αMT3 and Zn-βMT3 are all similar, and in all cases, the displacement of Zn( ii ) by Pb( ii ) is thermodynamically favorable. Zn-Replete and Pb-replete MT3 have distinctive circular dichroism spectra, suggestive of structural differences with different metallation status. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email