Thermodynamics and kinetics of a psychrophile frataxin variant

ERNESTO A. ROMAN

Castellón

Congreso; 6th International Iberian Biophysics Congress & X Iberoamerican Congress of Biophysics; 2018

Proteinsfrom a family share certain degree of sequence identity andstructural conservation, however thermodynamic and kineticcharacteristics are subtle coded. Frataxin proteins are around 7-10kcal/mol stable but depending on the variant particular signaturessuch as strong modulation of stability by pH.Herewe analyzed the correlation of thermodynamic stability anddifferent-timescales dynamics as function of pH. Previous resultsshowed that protein folds exchanging 2 protons and that pHstabilization comes mainly from entropic contributions.Titrationexperiments followed by NMR showed that pKa of ASP and GLU residuesfrom loop 1 are shifted with respect to their reference value. It wasalso found by CPMG and relaxation experiments that small shifts in pHchanges the entire dynamics from fast to slow motions (us to ms) andline broadening (seconds). Together with the chemical shiftperturbation and intensity changes, the existence of anotherconformational states under these conditions is suggested andsupported with the help of NOESY cross peaks and H-15NHSQCs at pHs around 8.Weconcluded that protonation and dynamics are linked and related tostability, and might be linked this frataxin?s psychrophilicnature. We discuss how subtle changes in this protein makes ittunable by pH.