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== '''MtrF''' ==

MtrF is a cell surface cytochrome that can play various roles in intermediating electron transfer straight to electron sinks, catalyzing electron exchange or partaking in extracellular intercytochrome electron exchange.(1) MtrF is a particular cell surface cytochrome on the bacteria known as Shewanella oneidensis. Certain bacterial species (Shewanella oneidensis) have the ability to utilize the extracellular mineral forms of Iron and Manganese as electron acceptors. This process requires three different proteins to move electrons across the cell membrane; this process ends in a decaheme cytochrome, mtrF, in Shewanella oneidensis.(2)

== '''MtrF Structure''' ==

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 7A from its neighbor, this close space allows for speedy electron transfer. (5) 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. (5) Domains I and III contain antiparallel Beta-strands that connect two Greek key split Beta-barrel domains. (5) Domains II and IV bind five closely packed hemes covalently attached Cys residues to the motifs in each domain. (5) 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 (5) The 3.2A crystal structure proposes that the hemes, each corresponding to two His ligands, are near enough for effective electron transfer. (2) Near-infrared magnetic circular dichroism and electron paramagnetic resonance spectroscopy provide additional support for these structural features. (2) The complete structure of MtrF is similar to an ellipsoid with dimensions of 85x70x30A. (5) 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. (1)

== '''MtrF’s role in Diseases''' ==

MtrF has been identified as a cell envelope protein that is involved with the resistance of hydrophobic antimicrobials in Neisseria Gonorrhoeae. MtrF is a protein that helps highlight the expression of detergent resistance by gonococci. MtrF is thought to act in accordance with the MtrC- MtrD- MtrE efflux pump; to make sure gonococci has high level resistance to specific hydrophobic agents. MtrF is located near the MtrR gene and is predicted to encode a cytoplasmic membrane protein that contains up to twelve transmembrane domains. The expression of MtrF is ultimately subject to MtrR’s transcriptional control. MtrF was given its name because it’s so closely tied to the protein MtrR. Several orthologues were discovered in a few Gram-negative and positive bacteria, indicating that perhaps the predicted products may represent an undescribed protein family that is highly involved with resistance of antimicrobials.(3)

== '''Regulation of MtrF''' ==

A prime example of MtrF regulation is the study of Regulation of mtrF Expression in Neisseria Gonorrhoeae and Its Role in High-Level Antimicrobial Resistance. In this study the expression of MtrF was repressed by MtrR (the major repressor in the mtrCDE expression). Another repressor known as MpeR can also regulate the expression of MtrF. Repression of MtrF by MtrR and MpeR was used, demonstrating that the repressive effects mediated by these regulators are independent processes. MtrF was also disabled and the significant reduction in the induction of hydrophobic agent resistance and it was found that the expression of MtrF is enhanced when gonococci are grown under inducing conditions.(4)

== '''References''' ==

1.) Crystal structure of the outer membrane decaheme cytochrome MtrF. 3PMQ. Protein Data Bank. http://www.pdb.org/pdb/explore/explore.do?structureId=3PMQ. Accessed November 26,2011.

2.) Clarke, Tom & Richardson, David. (20 Jun, 2011). Electron transport: Charting a heme conduit. Medica Journal.

http://medicajournal.com/chemical-biology/our-choices-from-the-recent-literature.html. Accessed November 28, 2011.

3.) Veal, Wendy L., & Shafer, William M. (28 Nov, 2002). Identification of a cell envelope protein (MtrF) involved in hydrophobic antimicrobial resistance in Neisseria gonorrhoeae.

Journal of Antimicrobial Chemotherapy. http://jac.oxfordjournals.org/content/51/1/27.full. Accessed November 28, 2011.

4.) Folster, Jason P., & Shafer, William M. (Jun 2005). Regulation of mtrF Expression in Neisseria Gonorrhoeae and Its Role in High-Level Antimicrobial Resistance. Journal of Bacteriology.

http://jb.asm.org/content/187/11/3713.full. Accessed November 28, 2011.

5.) Clarke, Thomas A., Edwards, Marcus A., 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. (22 Nov, 2010). Structure of a bacterial cell surface decaheme electron conduit. PNAS. http://www.pnas.org/cgi/doi/10.1073/pnas.1017200108. Accessed November 28, 2011.