Thermodynamic characterization of the folding process of Psychromonas ingrahamii?s frataxin (pFXN) by using calorimetry and circular dichroism.

BATASTINI NA; GONZALEZ-FLECHA FL; GONZALEZ-LEBRERO RM; ROMAN EA

CABA

Congreso; XLVIII Reunión Anual de la SAB; 2018

SAB

Despiteproteinsina family share certain degree of sequence identity and structuralconservation, theprocess by which each one reachesthe native structure maybe specifically and subtleregulated.Inthis sense, frataxinfamily showingageneral structural conservation but different celularroles betweeneukaryotes and prokaryotes, displayseveral foldingmechanism underthe same conditions.Frataxins are around 7-10 kcal/mol stable but depending on themolecularspeciespresent,particular signatures inits stability modulationwereobserved.Psychromonasingrahamii?sfrataxin (pFXN) shows apHdependence ofthe folding Gibbsfreeenergywhen going from pH 6 to 8. Themain goalofthis work is toperforma thermodynamic characterization of thepFXNfolding process and itspHandtemperature dependencies.Here,using isothermal titration calorimetry (ITC) we measurethe exchanged heat during pFXNfolding as a function of pH and temperature, andparallelly,secondary structure changes were registeredbyfar-UV ellipticitymeasurements.Ina firstapproach, the change in the measuredheat was analyzed in termsof threecomponents: theprotonation of thenativeand denatured states, and the folding ofthe protein.Theenthalpy change for this last process (dHf)was modeledasafirst order Taylor seriesof pH.Circulardichroism experiments yielded the native and denatured fractions ofpFXN as a function of pH at different temperatures and the number ofprotons involved in the process. This analysisalso allowedthecalculation of thedependency of the foldingentropy onpH.Our results points to an exhaustive characterization of the foldingprocess of pFXN with a robust thermodynamic description of theprocess yielding not only thefolding enthalpyand entropy but also theirderivativesrespect tothepH and the changesin heat capacity for the folding process and forbasalstates. PICT-2016,Ernesto Roman, AgenciaNacional dePromoción Científica yTecnológica.p { margin-bottom: 0.25cm; line-height: 120%; }a:link { }