4UCX: Structure Of The T18g Small Subunit Mutant Of D. Fructosovorans Nife-hydrogenase

Citation:
Abstract
The heterodimeric [NiFe] hydrogenase from Desulfovibrio fructosovorans catalyzes the reversible oxidation of H2 into protons and electrons. The catalytic intermediates have been attributed to forms of the active site (NiSI, NiR, and NiC) detected using spectroscopic methods under potentiometric but non-catalytic conditions. Here, we produced variants by replacing the conserved Thr-18 residue in the small subunit with Ser, Val, Gln, Gly, or Asp, and we analyzed the effects of these mutations on the kinetic (H2 oxidation, H2 production, and H/D exchange), spectroscopic (IR, EPR), and structural properties of the enzyme. The mutations disrupt the H-bond network in the crystals and have a strong effect on H2 oxidation and H2 production turnover rates. However, the absence of correlation between activity and rate of H/D exchange in the series of variants suggests that the alcoholic group of Thr-18 is not necessarily a proton relay. Instead, the correlation between H2 oxidation and production activity and the detection of the NiC species in reduced samples confirms that NiC is a catalytic intermediate and suggests that Thr-18 is important to stabilize the local protein structure of the active site ensuring fast NiSI-NiC-NiR interconversions during H2 oxidation/production.
PDB ID: 4UCXDownload
MMDB ID: 127130
PDB Deposition Date: 2014/12/5
Updated in MMDB: 2015/04
Experimental Method:
x-ray diffraction
Resolution: 1.95  Å
Source Organism:
Similar Structures:
Biological Unit for 4UCX: dimeric; determined by author and by software (PISA)
Molecular Components in 4UCX
Label Count Molecule
Proteins (2 molecules)
1
Hydrogenase (Nife) Small Subunit Hyda
Molecule annotation
1
Nickel-dependent Hydrogenase Large Subunit
Molecule annotation
Chemicals (13 molecules)
1
2
2
1
3
6
4
1
5
1
6
2
* Click molecule labels to explore molecular sequence information.

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