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pK(a) Values for the Unfolded State under Native Conditions Explain the pH-Dependent Stability of PGB1.

Lindman, Stina LU ; Bauer, Mikael LU ; Lund, Mikael LU ; Diehl, Carl LU ; Mulder, Frans LU ; Akke, Mikael LU and Linse, Sara LU (2010) In Biophysical Journal 99(10). p.3365-3373
Abstract
Understanding the role of electrostatics in protein stability requires knowledge of these interactions in both the folded and unfolded states. Electrostatic interactions can be probed experimentally by characterizing ionization equilibria of titrating groups, parameterized as pK(a) values. However, pK(a) values of the unfolded state are rarely accessible under native conditions, where the unfolded state has a very low population. Here, we report pK(a) values under nondenaturing conditions for two unfolded fragments of the protein G B1 domain that mimic the unfolded state of the intact protein. pK(a) values were determined for carboxyl groups by monitoring their pH-dependent (13)C chemical shifts. Monte Carlo simulations using a Gaussian... (More)
Understanding the role of electrostatics in protein stability requires knowledge of these interactions in both the folded and unfolded states. Electrostatic interactions can be probed experimentally by characterizing ionization equilibria of titrating groups, parameterized as pK(a) values. However, pK(a) values of the unfolded state are rarely accessible under native conditions, where the unfolded state has a very low population. Here, we report pK(a) values under nondenaturing conditions for two unfolded fragments of the protein G B1 domain that mimic the unfolded state of the intact protein. pK(a) values were determined for carboxyl groups by monitoring their pH-dependent (13)C chemical shifts. Monte Carlo simulations using a Gaussian chain model provide corrections for changes in electrostatic interactions that arise from fragmentation of the protein. Most pK(a) values for the unfolded state agree well with model values, but some residues show significant perturbations that can be rationalized by local electrostatic interactions. The pH-dependent stability was calculated from the experimental pK(a) values of the folded and unfolded states and compared to experimental stability data. The use of experimental pK(a) values for the unfolded state results in significantly improved agreement with experimental data, as compared to calculations based on model data alone. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biophysical Journal
volume
99
issue
10
pages
3365 - 3373
publisher
Cell Press
external identifiers
  • wos:000284438700031
  • pmid:21081085
  • scopus:78549261090
ISSN
1542-0086
DOI
10.1016/j.bpj.2010.08.078
language
English
LU publication?
yes
id
5620875e-802d-4258-ac78-d735fe707d76 (old id 1731919)
date added to LUP
2010-12-15 12:33:32
date last changed
2018-05-29 11:57:50
@article{5620875e-802d-4258-ac78-d735fe707d76,
  abstract     = {Understanding the role of electrostatics in protein stability requires knowledge of these interactions in both the folded and unfolded states. Electrostatic interactions can be probed experimentally by characterizing ionization equilibria of titrating groups, parameterized as pK(a) values. However, pK(a) values of the unfolded state are rarely accessible under native conditions, where the unfolded state has a very low population. Here, we report pK(a) values under nondenaturing conditions for two unfolded fragments of the protein G B1 domain that mimic the unfolded state of the intact protein. pK(a) values were determined for carboxyl groups by monitoring their pH-dependent (13)C chemical shifts. Monte Carlo simulations using a Gaussian chain model provide corrections for changes in electrostatic interactions that arise from fragmentation of the protein. Most pK(a) values for the unfolded state agree well with model values, but some residues show significant perturbations that can be rationalized by local electrostatic interactions. The pH-dependent stability was calculated from the experimental pK(a) values of the folded and unfolded states and compared to experimental stability data. The use of experimental pK(a) values for the unfolded state results in significantly improved agreement with experimental data, as compared to calculations based on model data alone.},
  author       = {Lindman, Stina and Bauer, Mikael and Lund, Mikael and Diehl, Carl and Mulder, Frans and Akke, Mikael and Linse, Sara},
  issn         = {1542-0086},
  language     = {eng},
  number       = {10},
  pages        = {3365--3373},
  publisher    = {Cell Press},
  series       = {Biophysical Journal},
  title        = {pK(a) Values for the Unfolded State under Native Conditions Explain the pH-Dependent Stability of PGB1.},
  url          = {http://dx.doi.org/10.1016/j.bpj.2010.08.078},
  volume       = {99},
  year         = {2010},
}