The Functional Unit of Neisseria Meningitidis 3-Deoxy-D-Arabino-Heptulosonate 7-Phosphate Synthase is Dimeric.Cross, P.J., Heyes, L.C., Zhang, S., Nazmi, A.R.
(2016) PLoS One 11: 45187
- PubMed: 26828675
- DOI: https://doi.org/10.1371/journal.pone.0145187
- Primary Citation of Related Structures:
- PubMed Abstract:
Neisseria meningitidis 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (NmeDAH7PS) adopts a homotetrameric structure consisting of an extensive and a less extensive interface. Perturbation of the less extensive interface through a single mutation of a salt bridge (Arg126-Glu27) formed at the tetramer interface of all chains resulted in a dimeric DAH7PS in solution, as determined by small angle X-ray scattering, analytical ultracentrifugation and analytical size-exclusion chromatography. The dimeric NmeDAH7PSR126S variant was shown to be catalytically active in the aldol-like condensation reaction between D-erythrose 4-phosphate and phosphoenolpyruvate, and allosterically inhibited by L-phenylalanine to the same extent as the wild-type enzyme. The dimeric NmeDAH7PSR126S variant exhibited a slight reduction in thermal stability by differential scanning calorimetry experiments and a slow loss of activity over time compared to the wild-type enzyme. Although NmeDAH7PSR126S crystallised as a tetramer, like the wild-type enzyme, structural asymmetry at the less extensive interface was observed consistent with its destabilisation. The tetrameric association enabled by this Arg126-Glu27 salt-bridge appears to contribute solely to the stability of the protein, ultimately revealing that the functional unit of NmeDAH7PS is dimeric.
Biomolecular Interaction Centre and Department of Chemistry, University of Canterbury, Christchurch, New Zealand.