Mechanisms for regulating electron transfer in multi-centre redox proteins.
Protein-mediated electron transfer is a key process in nature. Many of the proteins involved in such electron transfers are complex and contain a number of redox-active cofactors. The very complexity of these multi-centre redox proteins has made it difficult to fully understand the various electron transfer events they catalyse. This is sometimes because the electron transfer steps themselves are gated or coupled to other processes such as proton transfer. However, with the molecular structures of many of these proteins now available it is possible to probe these electron transfer reactions at the molecular level. It is becoming apparent that many of these multi-centre redox proteins have rather subtle and elegant ways for regulating electron transfer. The purpose of this article is to illustrate how nature has used different approaches to control electron transfer in a number of different systems. Illustrative examples include: thermodynamic control of electron transfer in flavocytochromes b(2) and P450 BM3; a novel control mechanism involving calmodulin-binding-dependent electron transfer in neuronal nitric oxide synthase; the probable gating of electron transfer by ATP hydrolysis in nitrogenase; conformational gating of electron transfer in cytochrome cd(1); the regulation of electron transfer by protein dynamics in the cytochrome bc(1) complex; and finally the coupling of electron transfer to proton transfer in cytochrome c oxidase.
Sharp
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Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA.
Chapman
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D000818:Animals; D001426:Bacterial Proteins; D001665:Binding Sites; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry; D003574:Cytochrome c Group; D003580:Cytochromes / Q000737:chemistry; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000737:chemistry; D003576:Electron Transport Complex IV / Q000737:chemistry; D007770:L-Lactate Dehydrogenase / Q000737:chemistry; D042844:L-Lactate Dehydrogenase (Cytochrome); D006899:Mixed Function Oxygenases / Q000737:chemistry; D009251:NADPH-Ferrihemoprotein Reductase; D019001:Nitric Oxide Synthase / Q000737:chemistry; D009572:Nitrite Reductases / Q000737:chemistry; D009591:Nitrogenase / Q000737:chemistry; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
D001426:Bacterial Proteins; D003574:Cytochrome c Group; D003580:Cytochromes; C019315:cytochrome cd1; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; D007770:L-Lactate Dehydrogenase; D042844:L-Lactate Dehydrogenase (Cytochrome); D019001:Nitric Oxide Synthase; D009591:Nitrogenase; D009251:NADPH-Ferrihemoprotein Reductase; C052423:flavocytochrome P450 BM3 monoxygenases; D009572:Nitrite Reductases; D003576:Electron Transport Complex IV; D014450:Electron Transport Complex III