Human frataxin (FXN) is a highly conserved mitochondrial protein involved in iron homeostasis and activation of the iron-sulfur cluster assembly. FXN deficiency causes the neurodegenerative disease Friedreich's Ataxia. Here, we investigated the effect of alterations in loop-1, a stretch presumably essential for FXN function, on the conformational stability and dynamics of the native state. We generated four loop-1 variants, carrying substitutions, insertions and deletions. All of them were stable and well-folded proteins. Fast local motions (ps-ns) and slower long-range conformational dynamics (μs-ms) were altered in some mutants as judged by NMR. Particularly, loop-1 modifications impact on the dynamics of a distant region that includes residues from the β-sheet, helix α1 and the C-terminal. Remarkably, all the mutants retain the ability to activate cysteine desulfurase, even when two of them exhibit a strong decrease in iron binding, revealing a differential sensitivity of these functional features to loop-1 perturbation. Consequently, we found that even for a small and relatively rigid protein, engineering a loop segment enables to alter conformational dynamics through a long-range effect, preserving the native-state structure and important aspects of function.
Insights on the conformational dynamics of human frataxin through modifications of loop-1 / Noguera, M. E.; Aran, M.; Smal, C.; Vazquez, D. S.; Herrera, M. G.; Roman, E. A.; Alaimo, N.; Gallo, M.; Santos, J.. - In: ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS. - ISSN 0003-9861. - 636(2017), pp. 123-137. [10.1016/j.abb.2017.10.022]
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