Difference between revisions of "Part:BBa K590034"

Revision as of 20:35, 24 October 2011

FabH2

This part encodes FabH2. [http://2011.igem.org/Team:Washington 2011 University of Washington iGEM Team] has produced even chain length alkanes using this part and the Petrobrick. In addition, expression of this part and the Petrobrick should theoretically produce branched chain alkanes, but we have not been able to demonstrate this effect, possibly due to the absence of the appropriate substrates in E. coli

Usage and Biology

FabH2 is from Bacillus subtilis. The FabH family of proteins initiates fatty acid elongation by converting an Acyl-CoA into an Acyl-ACP, with is extended by 2 carbon units to form longer chain length fatty acids. Normally, FabH proteins use a simple 2-carbon acetyl-CoA to start fatty acid biosynthesis, resulting in linear fatty acids. However, FabH2 can also use Isobutyryl-CoA, Isovaleryl-CoA, and 2-Methylbutyryl-CoA (products from Valine, Leucine, and Isoleucine degradation), resulting in 2-methyl branched fatty acid production. In addition, FabH2 has been hypothesized to start fatty acid elongation with a straight 3-carbon unit(propionyl-CoA), yielding odd chain length fatty acids, which could be converted into even chain length alkanes by thePetrobrick. Expression of FabH2 on the same high copy number constiuitive plasmid as the PetroBrick( as in Part BBa_K590030) results in slow cell growth( insert picture), and low alkane yield( under 10 mg/L vs. approximately 170 mg/L in the Petrobrick).

In order to reduce these toxic effects, we cloned FabH2 onto a low copy number PSB1C3 IPTG inducible PetroBrick . This construct was co-transformed with the Petrobrick in XL1-Blue E. coli. cells were grown up in rich TB media+ 5uM IPTG, and innocultated to OD10 in [ http://2011.igem.org/Team:Washington/alkanebiosynthesis#100mL_M9_minGlucose_Media_Prep M9 production media] + 5uM IPTG. Alkanes were extracted after 24 hours. In addition, GC runs were performed on uninduced FabH2/Petrobrick cultures, and on cells expressing only the PetroBrick.

GCMS trace confirming C16 alkane produced only upon FabBrick induction.

There was no significant difference between the GC peaks in the PetroBrick extract and in the uninduced FabH2/PetroBrick Extract. All of the peaks in these two extracts that fall within the expected elution time of the C16 alkane( 9.5-10 min) correspond to noise. When FabH2 is induced, we see a strong new peak at approximetly 9.75 minutes. The MS spectra of this peak is highly consistent with C16 alkane. The overall ion fragmentation fingerprint is identical to that alkane. Identification as a C16 alkane is confirmed by the presence of a strong parent ion at a mass of 226, exactly the mass of the C16 alkane. Both elution time and parent ion mass confirm that this new peak corresponds to the C16 alkane. In addition, some C14 alkane production was observed. This is the first time that even chain length alkanes have been produced recombinately, and expands the PetroBrick system to be able to produce all of the alkanes in the range C13-C17. Note that this peak corresponds to only trace levels of alkane( approximately 1mg/L), and future optimization is needed to increase even chain length production levels.

MS spectrum verifies peak contains C16 alkane.

Sequence and Features