Presentation Title

Ligand-dependent stability of CusF

Faculty Mentor

Blake Gillespie

Start Date

18-11-2017 2:15 PM

End Date

18-11-2017 3:15 PM

Location

BSC-Ursa Minor 35

Session

Poster 3

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

Although a protein's stability derives from its structure, ligands can also affect structure and stability. The bacterial copper chaperone CusF is stabilized via ligand binding of silver or copper ion, showing increased stability to thermal and chemical denaturation. We are investigating the thermodynamic mechanism of this stabilization through tryptophan fluorescence measurements of CusF unfolding behavior in the absence (apo) and presence (holo) of its ligand Ag(I). Stability curve analysis shows the temperature- and ligand dependence of enthalpy, entropy, and heat capacity of unfolding. We show that ligand binding increases CusF's unfolding enthalpy (Delta H) by approximately 5kcal-mol, its heat capacity (DCp) by 0.5kcal-mol, and its entropy (DS) by 30 cal-mol. Though the enthalpy change is the most obvious determinant of CusF's ligand-dependent stabilization, the mixed mechanism - particularly the heat capacity change - leaves open the possibility that CusF might show residual structure in the unfolded state of its holo-structure. Such residual structure would narrow the difference between folded and unfolded state heat capacities, resulting in a smaller DCp and a wider range of apparent thermal stability.

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Nov 18th, 2:15 PM Nov 18th, 3:15 PM

Ligand-dependent stability of CusF

BSC-Ursa Minor 35

Although a protein's stability derives from its structure, ligands can also affect structure and stability. The bacterial copper chaperone CusF is stabilized via ligand binding of silver or copper ion, showing increased stability to thermal and chemical denaturation. We are investigating the thermodynamic mechanism of this stabilization through tryptophan fluorescence measurements of CusF unfolding behavior in the absence (apo) and presence (holo) of its ligand Ag(I). Stability curve analysis shows the temperature- and ligand dependence of enthalpy, entropy, and heat capacity of unfolding. We show that ligand binding increases CusF's unfolding enthalpy (Delta H) by approximately 5kcal-mol, its heat capacity (DCp) by 0.5kcal-mol, and its entropy (DS) by 30 cal-mol. Though the enthalpy change is the most obvious determinant of CusF's ligand-dependent stabilization, the mixed mechanism - particularly the heat capacity change - leaves open the possibility that CusF might show residual structure in the unfolded state of its holo-structure. Such residual structure would narrow the difference between folded and unfolded state heat capacities, resulting in a smaller DCp and a wider range of apparent thermal stability.