期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 111, 期 2, 页码 611-616出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1316156111
关键词
respiration; density functional theory
资金
- Materials Chemistry Consortium from the Engineering and Physical Sciences Research Council [EP/F067496]
- Department of Energy Office of Biological and Environmental Research
- University College London
- PNNL through the US Department of Energy Office of Biological and Environmental Research Subsurface Biogeochemistry Research Science Focus Area program at PNNL
- University Research fellowship
- Engineering and Physical Sciences Research Council [EP/F067496/1] Funding Source: researchfish
- EPSRC [EP/F067496/1] Funding Source: UKRI
The naturally widespread process of electron transfer from metal reducing bacteria to extracellular solid metal oxides entails unique biomolecular machinery optimized for long-range electron transport. To perform this function efficiently, microorganisms have adapted multiheme c-type cytochromes to arrange heme cofactors into wires that cooperatively span the cellular envelope, transmitting electrons along distances greater than 100 angstrom. Implications and opportunities for bionanotechnological device design are self-evident. However, at the molecular level, how these proteins shuttle electrons along their heme wires, navigating intraprotein intersections and interprotein interfaces efficiently, remains a mystery thus far inaccessible to experiment. To shed light on this critical topic, we carried out extensive quantum mechanics/molecular mechanics simulations to calculate stepwise heme-to-heme electron transfer rates in the recently crystallized outer membrane deca-heme cytochrome MtrF. By solving a master equation for electron hopping, we estimate an intrinsic, maximum possible electron flux through solvated MtrF of 10(4)-10(5) s(-1), consistent with recently measured rates for the related multiheme protein complex MtrCAB. Intriguingly, our calculations show that the rapid electron transport through MtrF is the result of a clear correlation between heme redox potential and the strength of electronic coupling along the wire: thermodynamically uphill steps occur only between electronically well-connected stacked heme pairs. This observation suggests that the protein evolved to harbor low-potential hemes without slowing down electron flow. These findings are particularly profound in light of the apparently well-conserved staggered cross-heme wire structural motif in functionally related outer membrane proteins.
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