4QYT: Schizosaccharomyces pombe DJ-1

Cysteine residues with depressed pK(a) values are critical for the functions of many proteins. Several types of interactions can stabilize cysteine thiolate anions, including hydrogen bonds between thiol(ate)s and nearby residues as well as electrostatic interactions involving charged residues or dipoles. Dipolar stabilization of thiolates by peptide groups has been suggested to play a particularly important role near the N-termini of alpha-helices. Using a combination of X-ray crystallography, site-directed mutagenesis and spectroscopic methods, we show that the reactive cysteine residue (Cys111) in Schizosaccharomyces pombe DJ-1 experiences a 0.6 unit depression of its thiol pK(a) as a consequence of a hydrogen bond donated by a threonine side chain (Thr114) to a nearby peptide carbonyl oxygen at the N-terminus of an alpha-helix. This extended hydrogen bonded interaction is consistent with a sum of dipoles model whereby the distal hydrogen bond polarizes and strengthens the direct hydrogen bond between the proximal amide hydrogen and the cysteine thiol(ate). Therefore, our results suggest that the local dipolar enhancement of hydrogen bonds can appreciably stabilize cysteine thiolate formation. However, the substitution of a valine residue with a proline at the i + 3 position has only a minor effect (0.3 units) on the pK(a) of Cys111. As proline has a reduced peptide dipole moment, this small effect suggests that a more extended helix macrodipolar effect does not play a major role in this system.
PDB ID: 4QYTDownload
MMDB ID: 122238
PDB Deposition Date: 2014/7/25
Updated in MMDB: 2017/12
Experimental Method:
x-ray diffraction
Resolution: 1.05  Å
Source Organism:
Similar Structures:
Biological Unit for 4QYT: dimeric; determined by author and by software (PISA)
Molecular Components in 4QYT
Label Count Molecule
Proteins (2 molecules)
Uncharacterized Protein C22e12.03c(Gene symbol: SPAC22E12.03c)
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB