Structure-relaxation mechanism for the response of T4 lysozyme cavity mutants to hydrostatic pressure. Proc Natl Acad Sci U S A 2015 May 12;112(19):E2437-46
Date
04/29/2015Pubmed ID
25918400Pubmed Central ID
PMC4434698DOI
10.1073/pnas.1506505112Scopus ID
2-s2.0-84929164097 (requires institutional sign-in at Scopus site) 32 CitationsAbstract
Application of hydrostatic pressure shifts protein conformational equilibria in a direction to reduce the volume of the system. A current view is that the volume reduction is dominated by elimination of voids or cavities in the protein interior via cavity hydration, although an alternative mechanism wherein cavities are filled with protein side chains resulting from a structure relaxation has been suggested [López CJ, Yang Z, Altenbach C, Hubbell WL (2013) Proc Natl Acad Sci USA 110(46):E4306-E4315]. In the present study, mechanisms for elimination of cavities under high pressure are investigated in the L99A cavity mutant of T4 lysozyme and derivatives thereof using site-directed spin labeling, pressure-resolved double electron-electron resonance, and high-pressure circular dichroism spectroscopy. In the L99A mutant, the ground state is in equilibrium with an excited state of only ∼ 3% of the population in which the cavity is filled by a protein side chain [Bouvignies et al. (2011) Nature 477(7362):111-114]. The results of the present study show that in L99A the native ground state is the dominant conformation to pressures of 3 kbar, with cavity hydration apparently taking place in the range of 2-3 kbar. However, in the presence of additional mutations that lower the free energy of the excited state, pressure strongly populates the excited state, thereby eliminating the cavity with a native side chain rather than solvent. Thus, both cavity hydration and structure relaxation are mechanisms for cavity elimination under pressure, and which is dominant is determined by details of the energy landscape.
Author List
Lerch MT, López CJ, Yang Z, Kreitman MJ, Horwitz J, Hubbell WLAuthor
Michael Lerch PhD Assistant Professor in the Biophysics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Bacteriophage T4Circular Dichroism
Electron Spin Resonance Spectroscopy
Hydrogen-Ion Concentration
Hydrostatic Pressure
Ligands
Magnetic Resonance Spectroscopy
Models, Molecular
Muramidase
Mutagenesis, Site-Directed
Mutation
Protein Denaturation
Protein Folding
Protein Structure, Secondary
Solvents
Structure-Activity Relationship
Temperature
Thermodynamics