Tetramerization reinforces the dimer interface of MnSOD

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Yeast manganese superoxide dismutases (MnSOD) from Saccharomyces cerevisiae (ScMnSOD) and Candida albicans (CaMnSODc) share properties but differ in quaternary structure.
• ScMnSOD exists as a tetramer, while CaMnSODc is typically a dimer in solution, despite crystallizing as a tetramer.

Purpose of the Study:

• To investigate the functional significance of MnSOD quaternary structure.
• To analyze the impact of mutations at dimer interfaces on MnSOD oligomeric states and stability.

Main Methods:

• Analysis of wild-type and mutant forms of ScMnSOD and CaMnSODc.
• Assessment of oligomeric states, thermal stability, and resistance to denaturants and pH changes.

Main Results:

• Dimeric CaMnSODc exhibited greater susceptibility to thermal and denaturant-induced unfolding compared to tetrameric ScMnSOD.
• Mutations at dimer interfaces led to monomer dissociation in dimeric CaMnSODc but not in tetrameric ScMnSOD.

Conclusions:

• The tetrameric assembly significantly reinforces the dimer interface, which is crucial for MnSOD activity.
• Quaternary structure plays a vital role in MnSOD stability and function.