Part:BBa_K3763042

No part name specified with partinfo tag. ( The correct title should be: pFadD promoter with LacI repressor regulating downstream RFP)

Background

FadE, which is also called acyl-CoA dehydrogenases , catalyze the first reaction of the b-oxidation cycle. All acyl-CoA dehydrogenases carry noncovalently (but tightly) bound FAD, which is reduced during the oxidation of the fatty acid. As shown in Figure, FADH2 trans- fers its electrons to an electron transfer flavoprotein (ETF). Reduced ETF is reoxidized by a specific oxidoreductase (an iron–sulfur protein), which in turn sends the electrons on to the electron-transport chain at the level of coenzyme Q. The mitochondrial oxidation of FAD in this way eventually results in the net formation of about 1.5 ATPs. The mechanism of the acyl-CoA dehydrogenase involves deprotonation of the fatty acid chain at the a-carbon, followed by hydride transfer from the b-carbon to FAD.

Figure1. The FadE catalytic principlei.

Mechanism and Design

In our experiment, we hope to improve the expression of our engineered bacteria by overexpression of fade β-Oxidation capacity. As shown in the figure below, we constructed a recombinant plasmid containing FadE gene and introduced it into our engineered bacteria.

Figure2.Schematic diagram of recombinant vector containing FadE.

After confirming that we correctly constructed and transferred the recombinant plasmid into the engineering strain E. coli DH5 α, we used arabinose to induce the expression of FadE and tested its improvement on the fatty acid decomposition ability of engineered bacteria. Our experimental results showed that induced overexpression of FadE did not significantly improve the fatty acid decomposition ability of engineered bacteria, and did not reproduce the experimental results in references.

Figure1. Changes of fatty acid decomposition ability of engineering bacteria overexpressing FadE protein.

In order to explore the reasons for the failure of the experiment, we detected the protein expression more carefully. After inducing the expression of FadE proteins, they were purified by Ni2+ affinity chromatography column. After purification, SDS-PAGE results showed that the molecular weight of our target band was about 20 kDa lower than our predicted value. It is speculated that the engineering strain we used is E. coli DH5 α. The endogenous protease system of this strain has not been artificially knocked out, so the overexpressed protein is easy to be degraded. Considering this possibility, we replaced our engineered strain with E. coli BL21 strain. Then we purified the protein by Ni2+ affinity chromatography column and detected it by SDS-PAGE. The results showed that the bands of FadD and FadE protein were in line with our prediction.

Sequence and Features

Assembly Compatibility:

• 10
  INCOMPATIBLE WITH RFC[10]

  Illegal prefix found in sequence at 30
  Illegal suffix found in sequence at 230
  
• 12
  INCOMPATIBLE WITH RFC[12]

  Illegal EcoRI site found at 30
  Illegal SpeI site found at 231
  Illegal PstI site found at 245
  Illegal NotI site found at 36
  Illegal NotI site found at 238
  
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal EcoRI site found at 30
  
• 23
  INCOMPATIBLE WITH RFC[23]

  Illegal prefix found in sequence at 30
  Illegal suffix found in sequence at 231
  
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal prefix found in sequence at 30
  Illegal XbaI site found at 45
  Illegal SpeI site found at 231
  Illegal PstI site found at 245
  Illegal AgeI site found at 863
  Illegal AgeI site found at 975
  
• 1000
  COMPATIBLE WITH RFC[1000]