西亚试剂：Structure of a bacterial cell surface decaheme electron con

Structure of a bacterial cell surface decaheme electron conduit

Clarke, Thomas A.; Edwards, Marcus J.; Gates, Andrew J.; Hall, Andrea; White, Gaye F.; Bradley, Justin; Reardon, Catherine L.; Shi, Liang; Beliaev, Alexander S.; Marshall, Matthew J.; Wang, Zheming; Watmough, Nicholas J.; Fredrickson, James K.; Zachara, John M.; Butt, Julea N.; Richardson, David J.

Some bacterial species are able to utilize extracellular mineral forms of iron and manganese as respiratory electron acceptors.In Shewanella oneidensis this involves decaheme cytochromes that are located on the bacterial cell surface at the termini of trans-outer-membraneelectron transfer conduits. The cell surface cytochromes can potentially play multiple roles in mediating electron transferdirectly to insoluble electron sinks, catalyzing electron exchange with flavin electron shuttles or participating in extracellularintercytochrome electron exchange along “nanowire” appendages. We present a 3.2-? crystal structure of one of these decahemecytochromes, MtrF, that allows the spatial organization of the 10 hemes to be visualized for the first time. The hemes areorganized across four domains in a unique crossed conformation, in which a staggered 65-? octaheme chain transects the lengthof the protein and is bisected by a planar 45-? tetraheme chain that connects two extended Greek key split β-barrel domains.The structure provides molecular insight into how reduction of insoluble substrate (e.g., minerals), soluble substrates (e.g.,flavins), and cytochrome redox partners might be possible in tandem at different termini of a trifurcated electron transportchain on the cell surface.