1u9r
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| , resolution 2.10Å | |||||||
|---|---|---|---|---|---|---|---|
| Gene: | nuc (Staphylococcus aureus) | ||||||
| Activity: | Micrococcal nuclease, with EC number 3.1.31.1 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
Crystal Structure of Staphylococcal Nuclease mutant V66E/P117G/H124L/S128A at Room Temperature
OverviewOverview
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 17O and 2H 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.
About this StructureAbout this Structure
1U9R is a Single protein structure of sequence from Staphylococcus aureus. Full crystallographic information is available from OCA.
ReferenceReference
Stabilization of internal charges in a protein: water penetration or conformational change?, Denisov VP, Schlessman JL, Garcia-Moreno E B, Halle B, Biophys J. 2004 Dec;87(6):3982-94. Epub 2004 Sep 17. PMID:15377517
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