Part:BBa_K2302009
His＋Lpp-ompA＋L-FABP
This plasmid expresses a fatty acid binding protein that can be anchoredas a fused protein on the outer membrane. It consists of three basic parts: His, RBS, Lpp-OmpA, and L-FABP. Lpp-OmpA is a sequence encoding a functional peptide that allows surface anchoring of its fused FABP. FABP can bind long chain fatty acids. By transforming this plasmid, the host bacteria can catch long chain fatty acids in liquid and carry it on its outer membrane.
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21INCOMPATIBLE WITH RFC[21]Illegal XhoI site found at 462
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000INCOMPATIBLE WITH RFC[1000]Illegal BsaI.rc site found at 687
Design
FABP1 (L-FABP) is primarily expressed in the liver where it is involved in the binding, transport and metabolism of long-chain fatty acids. Lpp-ompA is a signal peptide that is used as an outer-membrane anchor for its fusion proteins in E. coli. Thus, proteins fused to OmpA-link are theoretically presented on the surface of bacteria. We combined the characteristic of FABP (bind to long-chain fatty acids) and Lpp-OmpA (anchor to the outer membrane of E. coli in our case. When the whole fusion protein was expressed, the signal peptide would lead the FABP to anchor onto the outer membrane of E. coli so that Follower E could bind fatty acids by the FABP expressed in the outer membrane of E. coli.
Experiment and Results
To confirm whether the pHisx6-Lpp-OmpA-FABP vector could successfully express the fusion protein, we used Western blot to analyze total bacterial proteins and cytomembrane proteins. The results showed that a protein with a size of predicted Lpp-OmpA-FABP fusion protein was clearly detected Follower E compared to the control group (Fig. 1A).Because Lpp-OmpA can anchor FABPs on the outer membrane, we determined whether FABP was present in the bacterial outer membrane. As we expected, FABP protein expression was steadily detected in outer membrane, but showed relatively low levels in cytoplasm (Fig. 1B). These results demonstrated that Lpp-OmpA could anchor FABP onto membrane; thus, pHisx6-Lpp-OmpA-FABP vector could work successfully, as we predicted.
Figure. 1. Western blot analysis of FABP protein expression in total bacteria (A) and cytomembrane (B). Con, empty pHisx6 vector; FABP, pHisx6-Lpp-OmpA-FABP overexpression plasmid; M, protein Molecular Weight Markers
To identify that the functional role of FABP in Follower E, the sample of broken bacteria solution binding with different concentrations of fatty acids was tested using a kit designated for free fatty acids detection.The results showed that Follower E could efficiently bind oleic acid (a type of fatty acids) in culture medium when compared to the control, and the binding capacity of Follower E was higher in the medium with 400 μM oleic acid than that with 200 μM oleic acid (Fig. 8). The result indicated that the FABP protein produced by Follower E could bind fatty acids as we designed.
Figure. 1. The binding capacity of Follower E at different concentrations of fatty acids.
Link
【1】http://2017.igem.org/Team:NEFU_China/Results:Followers
【2】http://2017.igem.org/Team:NEFU_China
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