High Apparent Dielectric Constants in the Interior of a Protein Reflect Water Penetration
| Autor: | Daniel A. Karp, Wesley E. Stites, Apostolos G. Gittis, John J. Dwyer, Daniel S. Spencer, Eaton E. Lattman, E Bertrand García-Moreno |
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| Rok vydání: | 2000 |
| Předmět: |
Models
Molecular Protein Denaturation Kinetics Biophysics Glutamic Acid Dielectric Crystal structure Crystallography X-Ray 01 natural sciences Protein Structure Secondary 03 medical and health sciences Polarizability 0103 physical sciences Molecule Micrococcal Nuclease Computer Simulation 030304 developmental biology 0303 health sciences 010304 chemical physics biology Chemistry Valine Penetration (firestop) Hydrogen-Ion Concentration Recombinant Proteins Solvent Crystallography Amino Acid Substitution Chemical physics biology.protein Mutagenesis Site-Directed Potentiometry Thermodynamics Micrococcal nuclease Research Article |
| Zdroj: | ResearcherID |
| ISSN: | 0006-3495 |
| DOI: | 10.1016/s0006-3495(00)76411-3 |
| Popis: | A glutamic acid was buried in the hydrophobic core of staphylococcal nuclease by replacement of Val-66. Its pK(a) was measured with equilibrium thermodynamic methods. It was 4.3 units higher than the pK(a) of Glu in water. This increase was comparable to the DeltapK(a) of 4.9 units measured previously for a lysine buried at the same location. According to the Born formalism these DeltapK(a) are energetically equivalent to the transfer of a charged group from water to a medium of dielectric constant of 12. In contrast, the static dielectric constants of dry protein powders range from 2 to 4. In the crystallographic structure of the V66E mutant, a chain of water molecules was seen that hydrates the buried Glu-66 and links it with bulk solvent. The buried water molecules have never previously been detected in >20 structures of nuclease. The structure and the measured energetics constitute compelling and unprecedented experimental evidence that solvent penetration can contribute significantly to the high apparent polarizability inside proteins. To improve structure-based calculations of electrostatic effects with continuum methods, it will be necessary to learn to account quantitatively for the contributions by solvent penetration to dielectric effects in the protein interior. |
| Databáze: | OpenAIRE |
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