Sandbox Reserved 386: Difference between revisions

MtrF as mentioned above is a decaheme cytochrome, which means that there are ten heme groups that are spatially organized throughout the protein. Each heme is spread about 7Å from its neighbor, this close space allows for speedy electron transfer. The (ten) hemes are organized across four domains in a distinctive cross conformation, a staggered 65-? Octaheme chain intersects the protein and is bisected by a planar 45-? Tetraheme chain. All of the hemes in the MtrF crystal structure display bis-His axial ligand coordination. The His residue in the domains provide the distal ligands for the five hemes in the same domain. Domains I and III contain antiparallel Beta-strands that connect two Greek key split Beta-barrel domains. Domains II and IV bind five closely packed hemes covalently attached Cys residues to the motifs in each domain. All the domains fold together so that the pentaheme domains II and IV are crowded together to form a central core with the two barrel domains I and III adjoining either side. The 3.2Å crystal structure proposes that the hemes, each corresponding to two His ligands, are near enough for effective electron transfer. Near-infrared magnetic circular dichroism and electron paramagnetic resonance spectroscopy provide additional support for these structural features. The complete structure of MtrF is similar to an ellipsoid with dimensions of 85x70x30Å. This particular structure was able to provide molecular insight into how the reduction of insoluble substrates, soluble substrates, and cytochrome redox partners may be possible together at different termini on an electron transport chain on the cell surface. .<ref> PMID:21606337 </ref>