INVESTIGADORES
GONZALEZ LEBRERO Mariano Camilo
artículos
Título:
A helix-coil transition induced by the metal ion interaction with a grafted iron-binding site of the CyaY protein family.
Autor/es:
DIEGO S. VAZQUEZ; AGUDELO, WILLIAM A.; ANGEL YONE; NORA VIZIOLI; MARTIN, ARÁN; GONZÁLEZ FLECHA, F. LUIS; GONZALEZ LEBRERO MC; SANTOS, JAVIER
Revista:
DALTON TRANSACTIONS
Editorial:
ROYAL SOC CHEMISTRY
Referencias:
Lugar: CAMBRIDGE; Año: 2015 p. 2370 - 2379
ISSN:
1477-9226
Resumen:
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 Fe3+ with a
moderate affinity (KD = 1.9 ± 0.2 μM) and a 1 : 1 stoichiometry. Remarkably, the GRAP/Fe3+ interaction is
entropically driven (ΔH° = −1.53 ± 0.03 kcal mol−1 and TΔS° = 6.26 kcal mol−1
). Experiments and simulationsindicate that Fe3+ 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