Exploring the dihydrodipicolinate synthase tetramer: how resilient is the dimer-dimer interface?

Area of Science:

• Biochemistry
• Enzymology
• Protein Structure

Background:

• Dihydrodipicolinate synthase (DHDPS) is a crucial enzyme in lysine biosynthesis.
• Its tetrameric structure is essential for optimal catalytic activity, likely by restricting aberrant protein motions present in dimeric variants.

Purpose of the Study:

• To investigate the role of the dimer-dimer interface in DHDPS tetramer stability and function.
• To determine the tolerance of DHDPS tetramerization to mutations within the interface.

Main Methods:

• Site-directed mutagenesis was employed to introduce amino acid substitutions at the dimer-dimer interface of DHDPS.
• The effects of these mutations on tetramer stability and enzyme catalytic activity were assessed.

Main Results:

• All introduced point mutations destabilized the tetrameric 'dimer of dimers' structure.
• Both mutation position and the physicochemical properties of the substituted amino acids influenced tetramerization.
• Even mutations causing only weak tetramer destabilization reduced catalytic activity to 10-15% of wild-type levels.

Conclusions:

• The dimer-dimer interface of DHDPS is finely tuned for optimal enzyme function.
• Alterations in this interface, even subtle ones, significantly impair catalytic efficiency, highlighting its critical role in maintaining enzyme dynamics and activity.