From Cold to Hot: A Temperature Analysis of the Quaternary Structure of the Enzyme Diaminopimelate Decarboxylase — ASN Events
  1. Schedule
  2. Session 10: Poster Session C
  3. From Cold to Hot: A Temperature Analysis of the Quaternary Structure of the Enzyme Diaminopimelate Decarboxylase

From Cold to Hot: A Temperature Analysis of the Quaternary Structure of the Enzyme Diaminopimelate Decarboxylase (#320)

Martin G. Peverelli 1 2 , Con Dogovski 2 , Matt A. Perugini 1 2
  1. Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia
  2. Department of Biochemistry & Molecular Biology, Bio21 Molecular Science & Biotechnology Institute, University of Melbourne, Melbourne, VIC 3010, Australia

The enzyme diaminopimelate decarboxylase (DAPDC) catalyses the final step of lysine biosynthesis in bacteria, plants and some fungi. In this reaction, meso-diaminopimelate is decarboxylated to form L-lysine. Both of these molecules are required for bacterial peptidoglycan cell wall synthesis, and lysine is also necessary for the production of housekeeping proteins and proteinaceous virulence factors. As such, the enzyme is a target for novel antibacterial design, given its absence in humans.

The crystal structures of DAPDC from eight bacterial and archaeal species display no obvious pattern of quaternary structure, with DAPDC forming monomers, dimers, and two different tetramer architectures. However, upon analysis with the server Protein Interfaces, Surfaces, and Assemblies (PISA), a pattern emerges. PISA predicts that DAPDC from the thermophilic species are tetrameric in solution, while DAPDC from the mesophilic species are dimeric. As most of the crystal structures were determined by structural genomic groups without additional biophysical analysis, the aim of this study was (1) to determine the biologically relevant quaternary structure of DAPDC in solution and (2) to probe the synergy between temperature and quaternary structure.

The experiments performed indicate that the biologically-relevant quaternary form of DAPDC is a dimer. The active recombinant enzymes from Escherichia coli, Bacillus anthracis, Mycobacterium tuberculosis, and Vibrio cholerae exist as dimers in solution as demonstrated by analytical ultracentrifugation and SAXS. Additionally, a R385A mutant of V. cholerae displays significant attenuation in dimerisation and catalytic function relative to the wild-type, which shows for the first time that dimerisation is critical for DAPDC function.

A comparative study between DAPDC from psychrophilic (i.e. cold), mesophilic (i.e. oderate), and thermophilic (i.e. hot) bacterial species demonstrate that the enzyme from the thermophile is tetrameric, whilst DAPDC  from the psychrophile and mesophiles are dimeric. Interestingly, the strength of dimerisation of DAPDC from the psychrophile is weaker contrasted to the enzymes from both the mesophiles and the thermophile. This study shows that a synergy exists between both the nature and  strength of quaternary structure of DAPDC from temperature extremophiles.