How to Charge a Battery

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Science  08 Mar 2002:
Vol. 295, Issue 5561, pp. 1789
DOI: 10.1126/science.295.5561.1789g

Many microorganisms live under anaerobic conditions and must use other oxidizing agents, usually by coupling the reduction of one metabolite to the oxidation of another. In Escherichia coli, one such redox loop involves nitrate reductase, which reduces nitrate to nitrite, and formate dehydrogenase, which oxidizes formate to carbon dioxide. The flow of electrons is itself used to pump protons across the plasma membrane and creates an electrochemical gradient that is essentially equivalent to a battery. Jormakka et al. (p. 1863; see the Perspective by Richardson and Sawers) present the crystal structure of the membrane protein formate dehydrogenase at 1.6 angstroms and describe how the electrons travel along a 90-angstrom chain of carriers from one side of the membrane to the other.

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