NDLI: A helix–coil transition induced by the metal ion interaction with a grafted iron-binding site of the CyaY protein family

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	González Lebrero, Mariano C. González Flecha, F. Luis Vazquez, Diego S. Vizioli, Nora Arán, Martín Santos, Javier Yone, Angel Agudelo, William A.
Description	Author Affiliation: Vazquez DS ( Instituto de Química y Físico - Química Biológicas, Universidad de Buenos Aires - CONICET, Junín 956, 1113AAD, Buenos Aires, Argentina. nanolebrero@gmail.com javiersantosw@gmail.com.)
Abstract	Iron–protein interactions are involved in electron transfer reactions. Alterations of these processes are present in a number of human pathologies; among them, in Friedreich's ataxia, in which a deficiency of functional frataxin, an iron-binding protein, leads to progressive neuromuscular degenerative disease. The putative iron-binding motif of acidic residues EExxED was selected from the first α-helical stretch of the frataxin protein family and grafted onto a foreign peptide scaffold corresponding to the C-terminal α-helix from E. coli thioredoxin. The resulting grafted peptide named GRAP was studied by applying experimental (circular dichroism, isothermal titration calorimetry, capillary zone electrophoresis, thermal denaturation, NMR) and computational approaches (docking, molecular dynamics simulations). Although isolated GRAP lacks a stable secondary structure in solution, when iron is added, the peptide acquires an α-helical structure. Here we have shown that the designed peptide is able to specifically bind $Fe^{3+}$ with a moderate affinity $(K_{D}$ = 1.9 ± 0.2 μM) and a 1:1 stoichiometry. Remarkably, the $GRAP/Fe^{3+}$ interaction is entropically driven (ΔH° = −1.53 ± 0.03 kcal $mol^{−1}$ and TΔS° = 6.26 kcal $mol^{−1}).$ Experiments and simulations indicate that $Fe^{3+}$ interacts with the peptide through three acidic side chains, inducing an α-helical conformation of the grafted motif. In addition, the acidic side chains involved undergo significant conformational rearrangements upon binding, as judged by the analysis of MDs. Altogether, these results contribute to an understanding of the iron-binding mechanisms in proteins and, in particular, in the case of human frataxin.
ISSN	14779226
Issue Number	5
Volume Number	44
e-ISSN	13645447
Journal	Dalton Trans.
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2015-02-07
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Escherichia Coli Proteins Chemistry Metabolism Iron Peptide Fragments Amino Acid Motifs Amino Acid Sequence Binding Sites Humans Pharmacology Molecular Dynamics Simulation Molecular Sequence Data Protein Structure, Secondary Drug Effects Journal Article Research Support, Non-U.S. Gov't
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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