3D6C

Crystal structure of Staphylococcal nuclease variant PHS L38E at cryogenic temperature


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • R-Value Free: 0.234 
  • R-Value Work: 0.173 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

The pK(a) values of acidic and basic residues buried at the same internal location in a protein are governed by different factors.

Harms, M.J.Castaneda, C.A.Schlessman, J.L.Sue, G.R.Isom, D.G.Cannon, B.R.Garcia-Moreno, E.B.

(2009) J.Mol.Biol. 389: 34-47

  • DOI: 10.1016/j.jmb.2009.03.039

  • PubMed Abstract: 
  • The pK(a) values of internal ionizable groups are usually very different from the normal pK(a) values of ionizable groups in water. To examine the molecular determinants of pK(a) values of internal groups, we compared the properties of Lys, Asp, and ...

    The pK(a) values of internal ionizable groups are usually very different from the normal pK(a) values of ionizable groups in water. To examine the molecular determinants of pK(a) values of internal groups, we compared the properties of Lys, Asp, and Glu at internal position 38 in staphylococcal nuclease. Lys38 titrates with a normal or elevated pK(a), whereas Asp38 and Glu38 titrate with elevated pK(a) values of 7.0 and 7.2, respectively. In the structure of the L38K variant, the buried amino group of the Lys38 side chain makes an ion pair with Glu122, whereas in the structure of the L38E variant, the buried carboxyl group of Glu38 interacts with two backbone amides and has several nearby carboxyl oxygen atoms. Previously, we showed that the pK(a) of Lys38 is normal owing to structural reorganization and water penetration concomitant with ionization of the Lys side chain. In contrast, the pK(a) values of Asp38 and Glu38 are perturbed significantly owing to an imbalance between favorable polar interactions and unfavorable contributions from dehydration and from Coulomb interactions with surface carboxylic groups. Their ionization is also coupled to subtle structural reorganization. These results illustrate the complex interplay between local polarity, Coulomb interactions, and structural reorganization as determinants of pK(a) values of internal groups in proteins. This study suggests that improvements to computational methods for pK(a) calculations will require explicit treatment of the conformational reorganization that can occur when internal groups ionize.


    Organizational Affiliation

    Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Thermonuclease
A
149Staphylococcus aureusGene Names: nuc
EC: 3.1.31.1
Find proteins for P00644 (Staphylococcus aureus)
Go to UniProtKB:  P00644
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CA
Query on CA

Download SDF File 
Download CCD File 
A
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
THP
Query on THP

Download SDF File 
Download CCD File 
A
THYMIDINE-3',5'-DIPHOSPHATE
C10 H16 N2 O11 P2
CSNCBOPUCJOHLS-XLPZGREQSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • R-Value Free: 0.234 
  • R-Value Work: 0.173 
  • Space Group: P 41
Unit Cell:
Length (Å)Angle (°)
a = 48.256α = 90.00
b = 48.256β = 90.00
c = 62.675γ = 90.00
Software Package:
Software NamePurpose
PHASERphasing
APEXdata collection
SAINTdata scaling
PDB_EXTRACTdata extraction
SAINTdata reduction
REFMACrefinement

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2008-11-04
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance
  • Version 1.2: 2018-01-24
    Type: Database references, Structure summary