Cold Enzymology Offers Insight into Molecular Evolution of Protein Quaternary Structure — ASN Events
  1. Schedule
  2. Session 5: Poster Session A
  3. Cold Enzymology Offers Insight into Molecular Evolution of Protein Quaternary Structure

Cold Enzymology Offers Insight into Molecular Evolution of Protein Quaternary Structure (#151)

Jacinta M Wubben 1 2 , Jason J Paxman 3 , Matthew T Downton 4 , Rachel Codd 5 , Michael W Parker 6 , John Wagner 4 , Con Dogovski 1 , Matthew A Perugini 1 2
  1. Biochemistry and Molecular Biology, The University of Melbourne, Parkville, VIC, Australia
  2. Biochemistry, La Trobe Institute for Molecular Science, Bundoora, VIC, Australia
  3. Australian Synchrotron, Clayton, VIC, Australia
  4. IBM Research Collaboratory for Life Sciences, Carlton, VIC, Australia
  5. School of Medical Sciences (Pharmacology), The University of Sydney, Camperdown, NSW, Australia
  6. St. Vincent's Institute for Medical Research, Fitzroy, VIC, Australia
Dihydrodipicolinate synthase (DHDPS) is a model oligomeric enzyme that has been shown to dimerise to complete the active site. However, DHDPS from mesophilic and thermophilic species adopts a dimer-of-dimers or tetrameric form in most cases, which is believed to have evolved to attenuate protein dynamics in the functional dimeric unit. Since protein dynamics are attenuated at cold temperatures, we hypothesise that DHDPS from a cold-dwelling species will exist in the minimal quaternary form required to support function, i.e. a dimer. This study reports the first structural characterisation of a cold (i.e. psychrophilic) DHDPS enzyme from the bacterium, Shewanella benthica (PsychroDHDPS), compared to mesophilic and thermophilic orthologs. A combination of circular dichroism spectroscopy (CD), X-ray crystallography, analytical ultracentrifugation (AUC), small angle X-ray scattering (SAXS), enzyme kinetics and molecular dynamics (MD) simulations were used to investigate the temperature-dependence on enzyme structure, function and dynamics. Consistent with the hypothesis, our study demonstrates that PsychroDHDPS exists as a functional dimer at biologically-relevant temperatures (≤12°C) both in solution and the crystalstate, but aggregates non-specifically with attenuated catalytic function at temperatures ≥20°C. This correlates with MD simulations demonstrating that temperature-dependent local fluctuations exist in a key catalytic residue that interdigitates between monomers to form the active dimer. Our results demonstrate a synergistic relationship betweenprotein oligomerisation, function and local dynamics for DHDPS, which offers insight into the molecular evolution ofenzyme quaternary structure and applications to industrial enzymology.