More Omc/Mtr deceheme cytochrome work

From the Shewanella gurus.  AFM analysis shows that MR-1 has an outer coating of decaheme cytochromes. Pretty neat stuff.

I’ve got a crazy idea… attach the lipid signal peptide of OmcA or MtrC to something like CymA and see if you can send it to the outer membrane.

Appl Environ Microbiol. 2009 Mar 13. [Epub ahead of print]

Antibody-recognition force microscopy shows that outer membrane cytochromes OmcA and MtrC are expressed on the exterior surface of Shewanella oneidensis MR-1.

Lower BH, Yongsunthon R, Shi L, Wildling L, Gruber HJ, Wigginton NS, Reardon CL,
Pinchuk GE, Droubay TC, Boily JF, Lower SK.

Antibody-recognition force microscopy showed that OmcA and MtrC are expressed on
the exterior surface of living Shewanella oneidensis MR-1 cells when Fe(III),
including solid phase hematite (Fe2O3), was the terminal electron acceptor. OmcA
was localized to the interface between the cell and mineral. MtrC displayed a
more uniform distribution across the cell surface. Both cytochromes were
associated with an extracellular polymeric substance.

PMID: 19286784 [PubMed - as supplied by publisher]

 

CymA and iron reductase activity?

Interesting paper on the tetraheme cytochrome has just been published. Authors show that the CymA cytochrome has iron reductase activity when expressed in E. coli. They propose that this has given E. coli the ability to respire iron(III). That is, E. coli can conserve energy from reducing iron and grow on it too. This is normally not the case. Here is the link to the paper in Pubmed:

Dissimilatory iron reduction in Escherichia coli: identification of CymA of Shewanella oneidensis and NapC of E. coli as ferric reductases.

Gescher JS, Cordova CD, Spormann AM.

http://www.ncbi.nlm.nih.gov/pubmed/18394146?dopt=Abstract

 

Isotopic labeling of Geobacter cytochromes

This looks like an interesting paper on N-15 labeling of c-type cytochromes:

Isotopic labeling of c-type multiheme cytochromes overexpressed in E. coli.
Fernandes et al. 2008

Progresses made in bacterial genome sequencing show a remarkable profusion of multiheme c-type cytochromes in many bacteria, highlighting the importance of these proteins in different cellular events. However, the characterization of multiheme cytochromes has been significantly retarded by the numerous experimental challenges encountered by researchers who attempt to overexpress these proteins, especially if isotopic labeling is required. Here we describe a methodology for isotopic labeling of multiheme cytochromes c overexpressed in Escherichia coli, using the triheme cytochrome PpcA from Geobacter sulfurreducens as a model protein. By combining different strategies previously described and using E. coli cells containing the gene coding for PpcA and the cytochrome c maturation gene cluster, an experimental labeling methodology was developed that is based on two major aspects: (i) use of a two-step culture growth procedure, where cell growth in rich media was followed by transfer to minimal media containing (15)N-labeled ammonium chloride, and (ii) incorporation of the heme precursor delta-aminolevulinic acid in minimal culture media. The yields of labeled protein obtained were comparable to those obtained for expression of PpcA in rich media. Proper protein folding and labeling were confirmed by UV-visible and NMR spectroscopy. To our knowledge, this is the first report of a recombinant multiheme cytochrome labeling and it represents a major breakthrough for functional and structural studies of multiheme cytochromes.

This looks really useful for making structure predictions or even looking at protein-protein interactions.

-chad