menaquinone-6 and molybdopterin-guanine-dinucleotide

The structure of the membrane protein formate dehydrogenase-N (Fdn-N), a major component of Escherichia coli nitrate respiration, has been determined at 1.6 angstroms. The structure demonstrates 11 redox centers, including molybdopterin-guanine dinucleotides, five [4Fe-4S] clusters, two heme b groups, and a menaquinone analog. These redox centers are aligned in a single chain, which extends almost 90 angstroms through the enzyme. The menaquinone reduction site associated with a possible proton pathway was also characterized. This structure provides critical insights into the proton motive force generation by redox loop, a common mechanism among a wide range of respiratory enzymes.

Topics: Binding Sites; Catalysis; Catalytic Domain; Cell Membrane; Crystallography, X-Ray; Electron Transport; Escherichia coli; Formate Dehydrogenases; Formates; Guanine Nucleotides; Hydrogen Bonding; Iron-Sulfur Proteins; Membrane Potentials; Models, Molecular; Nitrate Reductases; Oxidation-Reduction; Protein Conformation; Protein Structure, Quaternary; Protein Structure, Secondary; Protein Structure, Tertiary; Protein Subunits; Proton-Motive Force; Protons; Pterins; Vitamin K 2