IQUIBICEN   23947
INSTITUTO DE QUIMICA BIOLOGICA DE LA FACULTAD DE CIENCIAS EXACTAS Y NATURALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Contribution of water entropy to metal binding in Staphylococcus aureus transcription factor CzrA
Autor/es:
DI LELLA, SANTIAGO; BRINGAS, MAURO; CAPDEVILA, DAIANA
Reunión:
Congreso; XLIX Reunión Anual SAB; 2021
Institución organizadora:
SAB
Resumen:
CzrA is a transcription factor that regulates the response ofS. Aureus to high Zn(II) concentrations, and binds the metal with pM -1 affinity. Enthalpic (ΔH) and entropic (ΔS) binding contributions were characterized by calorimetry, and ΔS was dissected into ΔS conf -by means of sidechain dynamics NMR experiments- and ΔS solv -based on Cp changes of the system. Our aim is to validate the determination of ΔS solv for CzrA by Isothermal titration calorimetry (ITC) in D 2O and interpret at the atomistic level using computer simulations.We carried out ITC experiments at different temperatures in H2O buffers to obtain ΔCp anduse the ?cratic model? to estimate ΔS solv . In order to test the predictions from thisdetermination, we propose an alternative method to obtain this contribution independentfrom the assumptions of the cratic model. We propose to perform ITC experiments in D 2Obuffers, a strategy that has been used to determine enthalpic contributions of H2Omolecules in biomolecular association processes. Since those experiments also allow us toobtain changes in binding constants, we expect to estimate ΔS solv in a more directmanner. We expect a significant difference in ΔH contributions as the metal processoccurs coupled to proton release.Computational strategies allow us to complement the macroscopic estimation of ΔS solv ,since they enable us to estimate that same quantity in a site specific manner. We focus ontwo strategies to calculate entropy of H 2O molecules from molecular dynamicssimulations. In the first place we will calculate ΔS solv from protein-water radial distributionfunctions. This will allow us to characterize H 2O molecules that visit the surface of theprotein. In a second stage, we use a mutual information expansion strategy, consideringfirst, second and third order contributions to ΔS solv . This estimation allows us to map H 2Omolecules entropy in the whole simulation box. In both schemes we will compare S solv inZn-bound and unbound states of CzrA