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Stabilization of internal charges in a protein: Water penetration or conformational change?

Denisov, Vladimir LU ; Schlessman, J L; Garcia-Moreno E, B and Halle, Bertil LU (2004) In Biophysical Journal 87(6). p.3982-3994
Abstract
The ionizable amino acid side chains of proteins are usually located at the surface. However, in some proteins an ionizable group is embedded in an apolar internal region. Such buried ionizable groups destabilize the protein and may trigger conformational changes in response to pH variations. Because of the prohibitive energetic cost of transferring a charged group from water to an apolar medium, other stabilizing factors must be invoked, such as ionization-induced water penetration or structural changes. To examine the role of water penetration, we have measured the O-17 and H-2 magnetic relaxation dispersions (MRD) for the V66E and V66K mutants of staphylococcal nuclease, where glutamic acid and lysine residues are buried in... (More)
The ionizable amino acid side chains of proteins are usually located at the surface. However, in some proteins an ionizable group is embedded in an apolar internal region. Such buried ionizable groups destabilize the protein and may trigger conformational changes in response to pH variations. Because of the prohibitive energetic cost of transferring a charged group from water to an apolar medium, other stabilizing factors must be invoked, such as ionization-induced water penetration or structural changes. To examine the role of water penetration, we have measured the O-17 and H-2 magnetic relaxation dispersions (MRD) for the V66E and V66K mutants of staphylococcal nuclease, where glutamic acid and lysine residues are buried in predominantly apolar environments. At neutral pH, where these residues are uncharged, we find no evidence of buried water molecules near the mutation site. This contrasts with a previous cryogenic crystal structure of the V66E mutant, but is consistent with the room-temperature crystal structure reported here. MRD measurements at different pH values show that ionization of Glu-66 or Lys-66 is not accompanied by penetration of long-lived water molecules. On the other hand, the MRD data are consistent with a local conformational change in response to ionization of the internal residues. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biophysical Journal
volume
87
issue
6
pages
3982 - 3994
publisher
Cell Press
external identifiers
  • wos:000225426700034
  • pmid:15377517
  • scopus:10044267947
ISSN
1542-0086
DOI
10.1529/biophysj.104.048454
language
English
LU publication?
yes
id
6b9da9a8-860f-42e4-80db-27b72c04de55 (old id 141056)
date added to LUP
2007-06-29 09:13:52
date last changed
2017-01-01 04:39:18
@article{6b9da9a8-860f-42e4-80db-27b72c04de55,
  abstract     = {The ionizable amino acid side chains of proteins are usually located at the surface. However, in some proteins an ionizable group is embedded in an apolar internal region. Such buried ionizable groups destabilize the protein and may trigger conformational changes in response to pH variations. Because of the prohibitive energetic cost of transferring a charged group from water to an apolar medium, other stabilizing factors must be invoked, such as ionization-induced water penetration or structural changes. To examine the role of water penetration, we have measured the O-17 and H-2 magnetic relaxation dispersions (MRD) for the V66E and V66K mutants of staphylococcal nuclease, where glutamic acid and lysine residues are buried in predominantly apolar environments. At neutral pH, where these residues are uncharged, we find no evidence of buried water molecules near the mutation site. This contrasts with a previous cryogenic crystal structure of the V66E mutant, but is consistent with the room-temperature crystal structure reported here. MRD measurements at different pH values show that ionization of Glu-66 or Lys-66 is not accompanied by penetration of long-lived water molecules. On the other hand, the MRD data are consistent with a local conformational change in response to ionization of the internal residues.},
  author       = {Denisov, Vladimir and Schlessman, J L and Garcia-Moreno E, B and Halle, Bertil},
  issn         = {1542-0086},
  language     = {eng},
  number       = {6},
  pages        = {3982--3994},
  publisher    = {Cell Press},
  series       = {Biophysical Journal},
  title        = {Stabilization of internal charges in a protein: Water penetration or conformational change?},
  url          = {http://dx.doi.org/10.1529/biophysj.104.048454},
  volume       = {87},
  year         = {2004},
}