Characterization of a membrane-bound NADH-dependent Fe3+ reductase from the dissimilatory Fe3+-reducing bacterium Geobacter sulfurreducens

Geobacter sulfurreducens produces a single, membrane-associated Fe3+ reductase activity when grown on fumarate or Fe3+. The activity was initially isolated by solubilization of membranes with the non-ionic detergent dodecyl-beta-D-maltoside, and partially purified by a combination of ion exchange chromatography and preparative non-denaturing gel electrophoresis. Molecular mass of the reductase, as determined by gel filtration chromatography, was approximately 300 kDa. Cofactor analysis of the purified reductase demonstrates that it contains a hemoprotein and flavin adenine dinucleotide. Kinetic and inhibitor studies show thar the reductase is specific for NADH as electron donor, and confirm that the reductase enzymatically reduces Fe3+. The cytochrome associated with the complex undergoes a reoxidation upon addition of Fe3+ compounds, indicating an ability to pass reducing equivalents to Fe3+. This is the first description of a purified NADH-dependent Fe3+ reductase from a microorganism capable of coupling Fe3+ reduction to growth. (C) 2000 Published by Elsevier Science B.V. All rights reserved.