Frataxin from Psychromonas ingrahamii as a model to study stability modulation within the CyaY protein family

► Frataxin protein of an extreme psychrophilic organism was solved at 1.45 Å. ► The thermodynamic stability of this frataxin variant is strongly modulated by pH. ► B-factors show a differential flexibility in comparison to mesophilic homolog. ► The protonation state of His residues alters the protein motions. ► Electrostatic interactions may be involved in FXN adaptation to cold environments.