The Shewanella Blogger

Here is an interesting commentary on how the arsenic crisis in Bangladesh came to be. If the sources are true it’s an amazing story with a sad outcome:

http://www.unesco.org/courier/2001_01/uk/planet.htm

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

Suggested reading: “Shewanella secretes flavins that mediate extracellular electron transfer” by Bond and Gralnick labs. Here is the url: http://www.pnas.org/cgi/content/short/105/10/3968