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Dynamics, stability and iron‐binding activity of frataxin clinical mutants
Author(s) -
Correia Ana R.,
Pastore Chiara,
Adinolfi Salvatore,
Pastore Annalisa,
Gomes Cláudio M.
Publication year - 2008
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2008.06512.x
Subject(s) - frataxin , mutant , proteolysis , chemistry , ataxia , iron binding proteins , point mutation , biochemistry , biophysics , protein folding , mutation , mutant protein , wild type , protein aggregation , biology , gene , enzyme , neuroscience
Friedreich’s ataxia results from a deficiency in the mitochondrial protein frataxin, which carries single point mutations in some patients. In the present study, we analysed the consequences of different disease‐related mutations in vitro on the stability and dynamics of human frataxin. Two of the mutations, G130V and D122Y, were investigated for the first time. Analysis by CD spectroscopy demonstrated a substantial decrease in the thermodynamic stability of the variants during chemical and thermal unfolding (wild‐type > W155R > I154F > D122Y > G130V), which was reversible in all cases. Protein dynamics was studied in detail and revealed that the mutants have distinct propensities towards aggregation. It was observed that the mutants have increased correlation times and different relative ratios between soluble and insoluble/aggregated protein. NMR showed that the clinical mutants retained a compact and relatively rigid globular core despite their decreased stabilities. Limited proteolysis assays coupled with LC‐MS allowed the identification of particularly flexible regions in the mutants; interestingly, these regions included those involved in iron‐binding. In agreement, the iron metallochaperone activity of the Friedreich’s ataxia mutants was affected: some mutants precipitate upon iron binding (I154F and W155R) and others have a lower binding stoichiometry (G130V and D122Y). Our results suggest that, in heterozygous patients, the development of Friedreich’s ataxia may result from a combination of reduced efficiency of protein folding and accelerated degradation in vivo, leading to lower than normal concentrations of frataxin. This hypothesis also suggests that, although quite different from other neurodegenerative diseases involving toxic aggregation, Friedreich’s ataxia could also be linked to a process of protein misfolding due to specific destabilization of frataxin.