Molecular evolution of an oligomeric biocatalyst functioning in lysine biosynthesis

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Dihydrodipicolinate synthase (DHDPS) is a crucial enzyme in the diaminopimelate (DAP) pathway, essential for lysine biosynthesis in bacteria and plants.
• The dapA gene encoding DHDPS is vital for bacterial and plant survival, making DHDPS a significant target for research.
• DHDPS exhibits allosteric inhibition by lysine in plants and some bacteria, with specific amino acid residues influencing this regulation.

Purpose of the Study:

• To elucidate the function, regulation, and structure of DHDPS, a key class I aldolase.
• To investigate the structural differences between bacterial and plant DHDPS enzymes, particularly their quaternary arrangements.
• To explore the potential role of pyruvate in stabilizing DHDPS structure and function.

Main Methods:

• Analytical ultracentrifugation
• Small-angle X-ray scattering (SAXS)
• Macromolecular crystallography

Main Results:

• DHDPS monomers form active sites binding pyruvate and (S)-aspartate β-semialdehyde.
• Bacterial DHDPS tetramers adopt a head-to-head quaternary structure.
• Plant DHDPS enzymes display a back-to-back quaternary arrangement.

Conclusions:

• Structural and biophysical studies reveal distinct quaternary architectures of bacterial and plant DHDPS.
• Understanding these structural differences can inform the development of targeted inhibitors.
• Pyruvate may play a role in substrate-mediated stabilization of DHDPS, impacting enzyme activity.