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Electrostatic optimization of the conformational energy landscape in a metamorphic protein. Biochemistry 2012 Nov 13;51(45):9067-75

Date

10/30/2012

Pubmed ID

23102260

Pubmed Central ID

PMC3567213

DOI

10.1021/bi300842j

Scopus ID

2-s2.0-84869078793   8 Citations

Abstract

The equilibrium unfolding reaction of Ltn, a metamorphic C-class chemokine, was monitored by tryptophan fluorescence to determine unfolding free energies. Measurements revealed that addition of 150 mM NaCl stabilized the Ltn chemokine fold by approximately 1 kcal/mol. Specific mutations involving Arg23 and Arg43 also increased the stability by 1 kcal/mol, suggesting their involvement in chloride ion coordination. This interaction was confirmed by nuclear magnetic resonance (NMR) salt titration studies that revealed chemical shift perturbations localized to these residues and backbone amides within the proximal 40s loop. The effects of NaCl on the free energy landscape were further verified by ZZ-exchange NMR spectroscopy. Our results suggest that changes in the electrostatic environment modulate the Gibbs free energy of folding and alter the forward and reverse rates of interconversion. These results demonstrate how solution ions can promote metamorphic folding by adjusting the relative stabilities of two unrelated Ltn native-state structures.

Author List

Tyler RC, Wieting JC, Peterson FC, Volkman BF

Authors

Francis C. Peterson PhD Professor in the Biochemistry department at Medical College of Wisconsin
Brian F. Volkman PhD Professor in the Biochemistry department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Binding Sites
Chemokines, C
Chlorides
Humans
Kinetics
Mutation
Nuclear Magnetic Resonance, Biomolecular
Protein Conformation
Protein Denaturation
Protein Stability
Sodium Chloride
Static Electricity
Thermodynamics
Tryptophan
jenkins-FCD Prod-444 eb4ebd1a08581aba961d3befd3b851a3c3ec6b46