title: Manganese activation of superoxide dismutase 2 in the mitochondria of Saccharomyces cerevisiae.
abstract: Manganese-dependent superoxide dismutase 2 (SOD2) in the mitochondria plays a key role in protection against oxidative stress. Here we probed the pathway by which SOD2 acquires its manganese catalytic cofactor. We found that a mitochondrial localization is essential. A cytosolic version of Saccharomyces cerevisiae Sod2p is largely apo for manganese and is only efficiently activated when cells accumulate toxic levels of manganese. Furthermore, Candida albicans naturally produces a cytosolic manganese SOD (Ca SOD3), yet when expressed in the cytosol of S. cerevisiae, a large fraction of Ca SOD3 also remained manganese-deficient. The cytosol of S. cerevisae cannot readily support activation of Mn-SOD molecules. By monitoring the kinetics for metalation of S. cerevisiae Sod2p in vivo, we found that prefolded Sod2p in the mitochondria cannot be activated by manganese. Manganese insertion is only possible with a newly synthesized polypeptide. Furthermore, Sod2p synthesis appears closely coupled to Sod2p import. By reversibly blocking mitochondrial import in vivo, we noted that newly synthesized Sod2p can enter mitochondria but not a Sod2p polypeptide that was allowed to accumulate in the cytosol. We propose a model in which the insertion of manganese into eukaryotic SOD2 molecules is driven by the protein unfolding process associated with mitochondrial import.
authors.affiliation: Environmental Health Sciences and Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205, USA.
authors.forename: Edward
authors.initials: E
authors.lastname: Luk
authors.forename: Mei
authors.initials: M
authors.lastname: Yang
authors.forename: Laran T
authors.initials: LT
authors.lastname: Jensen
authors.forename: Yves
authors.initials: Y
authors.lastname: Bourbonnais
authors.forename: Valeria Cizewski
authors.initials: VC
authors.lastname: Culotta
mesh_terms: D000595:Amino Acid Sequence; D002176:Candida albicans / Q000201:enzymology; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008345:Manganese / Q000737:chemistry / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011489:Protein Denaturation; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism*; D013997:Time Factors; D000099156:Superoxide Dismutase 2
chemical_list: D008345:Manganese; D010455:Peptides; D013482:Superoxide Dismutase; D000099156:Superoxide Dismutase 2