title: Tetramerization reinforces the dimer interface of MnSOD.
abstract: Two yeast manganese superoxide dismutases (MnSOD), one from Saccharomyces cerevisiae mitochondria (ScMnSOD) and the other from Candida albicans cytosol (CaMnSODc), have most biochemical and biophysical properties in common, yet ScMnSOD is a tetramer and CaMnSODc is a dimer or "loose tetramer" in solution. Although CaMnSODc was found to crystallize as a tetramer, there is no indication from the solution properties that the functionality of CaMnSODc in vivo depends upon the formation of the tetrameric structure. To elucidate further the functional significance of MnSOD quaternary structure, wild-type and mutant forms of ScMnSOD (K182R, A183P mutant) and CaMnSODc (K184R, L185P mutant) with the substitutions at dimer interfaces were analyzed with respect to their oligomeric states and resistance to pH, heat, and denaturant. Dimeric CaMnSODc was found to be significantly more subject to thermal or denaturant-induced unfolding than tetrameric ScMnSOD. The residue substitutions at dimer interfaces caused dimeric CaMnSODc but not tetrameric ScMnSOD to dissociate into monomers. We conclude that the tetrameric assembly strongly reinforces the dimer interface, which is critical for MnSOD activity.
authors.affiliation: Department of Chemistry, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Yuewei
authors.initials: Y
authors.lastname: Sheng
authors.forename: Armando
authors.initials: A
authors.lastname: Durazo
authors.forename: Mikhail
authors.initials: M
authors.lastname: Schumacher
authors.forename: Edith Butler
authors.initials: EB
authors.lastname: Gralla
authors.forename: Duilio
authors.initials: D
authors.lastname: Cascio
authors.forename: Diane E
authors.initials: DE
authors.lastname: Cabelli
authors.forename: Joan Selverstone
authors.initials: JS
authors.lastname: Valentine
mesh_terms: D000595:Amino Acid Sequence; D002176:Candida albicans / Q000166:cytology; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D004795:Enzyme Stability; D006358:Hot Temperature; D008928:Mitochondria / Q000201:enzymology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011489:Protein Denaturation; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D012441:Saccharomyces cerevisiae / Q000166:cytology; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D013482:Superoxide Dismutase