Thermodynamics and kinetics of a psychrophile frataxin variant

GONZALEZ-LEBRERO RM; NOGUERA, MARTÍN E.; DEFELIPE, LUCAS; SANTOS J; FABIO ALMEIDA; IQBAL, ANWAR; ROMAN, ERNESTO A.

Castellon

Congreso; 6th International Iberian Byophysics Congress/ X Iberoamerican Congress of Biophysics; 2019

Sociedad de Biofisica de Espana

Proteins from a family share certain degree of sequence identity and structural conservation,however thermodynamic and kinetic characteristics are subtle coded. Frataxin proteins are around7-10 kcal/mol stable but depending on the variant particular signatures such as strong modulationof stability by pH. Here we analyzed the correlation of thermodynamic stability and differenttimescales dynamics as function of pH. Previous results showed that protein folds exchanging 2protons and that pH stabilization comes mainly from entropic contributions. Titration experimentsfollowed by NMR showed that pKa of ASP and GLU residues from loop 1 are shifted with respectto their reference value. It was also found by CPMG and relaxation experiments that small shiftsin pH changes the entire dynamics from fast to slow motions (us to ms) and line broadening(seconds). Together with the chemical shift perturbation and intensity changes, the existence ofanother conformational states under these conditions is suggested and supported with the help ofNOESY cross peaks and H-15N HSQCs at pHs around 8. We concluded that protonation anddynamics are linked and related to stability, and might be linked this frataxin?s psychrophilic nature.We discuss how subtle changes in this protein makes it tunable by pH.