Abstract:
:A method for combining calculations of residue pKa's with changes in the position of polar hydrogens has been developed. The Boltzmann distributions of proton positions in hydroxyls and neutral titratable residues are found in the same Monte Carlo sampling procedure that determines the amino acid ionization states at each pH. Electrostatic, Lennard-Jones potentials, and torsion angle energies are considered at each proton position. Many acidic and basic residues are found to have significant electrostatic interactions with either a water- or hydroxyl-containing side chain. Protonation state changes are coupled to reorientation of the neighboring hydroxyl dipoles, resulting in smaller free energy differences between neutral and ionized residues than when the protein is held rigid. Multiconformation pH titration gives better agreement with the experimental pKa's for triclinic hen egg lysozyme than conventional rigid protein calculations. The hydroxyl motion significantly increases the protein dielectric response, making it sensitive to the composition of the local protein structure. More than one conformer per residue is often found at a given pH, providing information about the distribution of low-energy lysozyme structures.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Alexov EG,Gunner MRdoi
10.1016/S0006-3495(97)78851-9subject
Has Abstractpub_date
1997-05-01 00:00:00pages
2075-93issue
5eissn
0006-3495issn
1542-0086pii
S0006-3495(97)78851-9journal_volume
72pub_type
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