2NU9: C123at Mutant Of E. Coli Succinyl-Coa Synthetase Orthorhombic Crystal Form

Succinyl-CoA synthetase has a highly conserved cysteine residue, Cys123alpha in the Escherichia coli enzyme, that is located near the CoA-binding site and the active-site histidine residue. To test whether the succinyl moiety of succinyl-CoA is transferred to the thiol of Cys123alpha as part of the catalytic mechanism, this residue was mutated to alanine, serine, threonine and valine. Each mutant protein was catalytically active, although less active than the wild type. This proved that the specific formation of a thioester bond with Cys123alpha is not part of the catalytic mechanism. To understand why the mutations affected catalysis, the crystal structures of the four mutant proteins were determined. The alanine mutant showed no structural changes yet had reduced activity, suggesting that the size of the cysteine is important for optimal activity. These results explain why this cysteine residue is conserved in the sequences of succinyl-CoA synthetases from different sources.
PDB ID: 2NU9Download
MMDB ID: 53894
PDB Deposition Date: 2006/11/8
Updated in MMDB: 2012/10
Experimental Method:
x-ray diffraction
Resolution: 2.9  Å
Source Organism:
Similar Structures:
Biological Unit for 2NU9: tetrameric; determined by author and by software (PISA)
Molecular Components in 2NU9
Label Count Molecule
Proteins (4 molecules)
Succinyl-coa Ligase [adp-forming] Subunit Alpha(Gene symbol: sucD)
Molecule annotation
Succinyl-coa Synthetase Beta Chain(Gene symbol: sucC)
Molecule annotation
Chemicals (8 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB