tailieunhanh - Báo cáo khoa học: Methanoferrodoxin represents a new class of superoxide reductase containing an iron–sulfur cluster

Protein MM0632 from the methanogenic archaeonMethanosarcina 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 cytochromecassay and in a test system with NADPH, ferredoxin:NADP + reductase, and rubredoxin. | IFEBS Journal Methanoferrodoxin represents a new class of superoxide reductase containing an iron-sulfur cluster Christian Kratzer1 Cornelia Welte1 Katerina Dorner2 Thorsten Friedrich2 and Uwe Deppenmeier1 1 Institut fur Mikrobiologie und Biotechnologie Universitat Bonn Germany 2 Institut fur Organische Chemie und Biochemie Albert-Ludwigs-Universitat Freiburg Germany Keywords detoxification iron-sulfur protein methanogenic archaea oxygen radicals superoxide dismutase Correspondence U. Deppenmeier Institut fur Mikrobiologie und Biotechnologie Universitat Bonn Meckenheimer Allee 168 53115 Bonn Germany Fax 49 228737576 Tel 49 228735590 E-mail udeppen@ Received 5 October 2010 revised 8 November 2010 accepted 17 November 2010 doi 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. Introduction Oxidative stress is caused by reactive oxygen species such as hydrogen peroxide H2O2 the hydroxyl radical OH and the superoxide anion