Methanoferrodoxin represents a new class of superoxide reductase containing an iron-sulfur cluster.
Protein MM0632 from the methanogenic archaeon Methanosarcina mazei showed strong superoxide reductase activity and rapidly decomposed superoxide radicals to peroxides. The superoxide reductase activity of the heterologously produced enzyme was determined by a cytochrome c assay and in a test system with NADPH, ferredoxin:NADP(+) reductase, and rubredoxin. Furthermore, EPR spectroscopy showed that MM0632 is the first superoxide reductase that possesses an iron-sulfur cluster instead of a second mononuclear iron center. We propose the name methanoferrodoxin for this new class of superoxide reductase with an [Fe(NHis)(4)(SCys)] site as the catalytic center and a [4Fe-4S] cluster as second prosthetic group that is probably involved in electron transfer to the catalytic center. Methanosarcina mazei grows only under anaerobic conditions, but is one of the most aerotolerant methanogens. It is tempting to speculate that methanoferrodoxin contributes to the protection of cells from oxygen radicals formed by flavoproteins during periodic exposure to oxygen in natural environments.
Institut für Mikrobiologie und Biotechnologie, Universität Bonn, Germany.
Christian
C
Krätzer
Cornelia
C
Welte
Katerina
K
Dörner
Thorsten
T
Friedrich
Uwe
U
Deppenmeier
D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D004578:Electron Spin Resonance Spectroscopy; D005288:Ferredoxins / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D017020:Methanosarcina / Q000201:enzymology*; D009249:NADP / Q000378:metabolism; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism
D019843:Archaeal Proteins; D005288:Ferredoxins; D007506:Iron-Sulfur Proteins; D009249:NADP; D010088:Oxidoreductases; C121849:superoxide reductase