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.