Part:BBa_K2027001
AE Blue-CBD-FlagLumioHisTag Fusion Protein
This part was created using a synthetically produced chromoprotein from the DNA2.0 chromoprotein paintbox [1] and adding a cellulose binding domain from the iGEM registry (BBa_K1321366) and a FLAG, lumino and 6x histidine tag.
Learn more about our chromoprotein collection here: http://2016.igem.org/Team:Stanford-Brown/SB16_BioSensor_Chromoproteins.
Why Monitor Temperature?
On Earth, vertical temperature profiles can be obtained using electronic temperature sensors mounted on weather balloons. These balloons go up to different heights in the atmosphere and relay real-time measurements of the atmospheric temperatures. While these electronics are easy to obtain and replace if they are broken on Earth, in the context of planetary exploration, they are irreplaceable and unreliable because it would take years to send replacements if they break and are impossible to fix without also sending replacement parts along the mission. Thus, a biological temperature sensor was developed in order to address these concerns. This biological temperature sensor can be expressed in a small culture of </i>E. coli</i> and be easily replaced simply by maintaining a culture of that particular bacteria.
Closed System: chromoproteins in vivo
<figure class="fig"><img src="" class="img-L"> <figcaption>Figure 6</figcaption></figure>
<figure class="fig"><img src="" class="img-L"> <figcaption>Figure 7</figcaption></figure>
Twelve chromoproteins that were expressing good color in our cultures were selected for this assay and can be seen below in Figure 9. After this, the glass petri dish was removed from heat and 20 µL of DI water were added to each of the chromoproteins. This was done on the theory that the chromoproteins had not denatured, but rather had lost their color because all of the water molecules which were supporting the structure of their barrel had been driven out by the heat. As can be seen in the image below, some of the chromoproteins regained color when water was added, but this color is different from the starting color. This could be due to the fact that the heating caused the chromoprotein structure to destabilize to a lower energy structure which causes it to have a different color when the water is added to support the barrel.
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<figcaption>Figure 8: Setup for conducting temperature testing on chromoproteins.</figcaption></figure>
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<figcaption>Figure 9: 30 µL droplets of cell lysate taken from spun down 5 mL cultures of cells expressing chromoproteins were placed on a glass petri dish. Order of Chromoproteins:
Top row: VixenPurple
Second row: asPink, tsPurple, AE Blue
Third row: TinselPurple, CupidPink, PrancerPurple, DreidelTeal
Fourth row: spisPink, scOrange, BlitzenBlue
Fifth row: DonnerMagenta
</figcaption></figure>
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<figcaption>Figure 10: The glass petri dish above was heated to 85 °C which caused all of the chromoproteins to lose their color as is seen below. </figcaption></figure>
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<figcaption>Figure 11: Chromoproteins from figure 10 after being brought back to room temperature. </figcaption></figure>
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<figcaption>Figure 12 </figcaption></figure>
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<figcaption>Figure 13: Two replicates of PrancerPurple (top) and ScroogeOrange (bottom) are shown after 1 hour of lyophilization. </figcaption></figure>
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<figcaption>Figure 14</figcaption></figure>
<figure class="fig"><img src="" class="img-L"> <figcaption>Figure 15 </figcaption></figure>
<figure class="fig"><img src="" class="img-L"> <figcaption>Figure 16 </figcaption></figure>
Open System: purified chromoproteins
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<figcaption>Figure 17: The Gibson Assembly Process for creating tagged chromoprotein constructs.</figcaption></figure>
To delve further into the question of what exactly is happening when these chromoproteins are heated, we used Gibson Assembly to clone the gene coding for the iGEM biobrick AE Blue and the 12 DNA2.0 chromoproteins into pSB1C3. We also added a FLAG, lumino and 6x histidine tag in order be able to extract the expressed protein using nickel column purification. The lumino tag is a specific six amino acid sequence that binds to the <a href=https://www.thermofisher.com/order/catalog/product/LC6090>LumioTM Green</a> [4] which allows the fusion of the lumino tag and the chromoprotein to be detected on an SDS-Page Gel without having to run a staining protocol. The FLAG tag allows for anything after its sequence to be cleaved off of the protein when the extracted protein is incubated with enterokinase [5].This was done in case the lumino or histidine tag interfered with the chromoprotein structure.
The extracted protein was concentrated using microfiltration tubes then allowed to dry on cellulose sheets which had wax wells printed on them. These cellulose sheets with the dried chromoprotein were then placed in a preheated oven and the temperature was increased at five minute intervals until a temperature change was observed.
Prototyping a biological thermometer
<figure class="fig"><img src="" class="img-L"> <figcaption>Figure 18: Gel run of our chromoproteins and Flag-Lumino His tag. Ladder(left), DonnerMagenta, VirginiaViolet, ScroogeOrange, LeorOrange, DreidelTeal, VixenPurple, SeraphinaPink, CupidPink, TinselPurple, PrancerPurple, MaccabeePurple, BlitzenBlue </figcaption></figure>
<figure class="fig"><img src="" class="img-L"> <figcaption>Figure 19: Chromoproteins before heat. Order is (top to bottom), CupidPink, PrancerPurple, TinselPurple, and VixenPurple </figcaption></figure>
<figure class="fig"><img src="" class="img-L"> <figcaption>Figure 20: Chromoproteins after heat </figcaption></figure>
<figure class="fig"><img src="" class="img-L"> <figcaption>Figure 21: Chromoproteins after water has been added </figcaption></figure>
We were then able to move into heat testing of all 12 DNA2.0 chromoproteins with FLAG lumino his-tags. We pipetted 3 µl of extracted protein into each well and then let dry and added another 3 µl as seen in Figure 22. Once this was dry we placed it into the oven that was preheated at 20 °C. We then began raising the temperature a degree C at a time until all 12 chromoproteins had lost their color Figure 16. This process took an hour and the temperature was raised from 20 °C to 60 °C over this time period. The chromoprotein and the temperature it lost its color at is: PrancerPurple (55 °C), CupidPink (47 °C), TinselPurple (48 °C), VixenPurple (50 °C), MaccabeePurple (55 °C), SeraphinaPink (47 °C), LeorOrange (57 °C), ScroogeOrange (56 °C), BlitzenBlue (60 °C), DreidelTeal (Not colored in this experiment so no color changed observed), DonnerMagenta (55 °C), VirginiaViolet (53 °C). The chromoproteins were then taken out of the oven and rehydrated with 3 µl of milliQ water and they regained color Figure 23. We then added a second set of wells with chromoproteins by again pipetting 3 µl into a well, letting it dry and adding another 3 µl to the well. We tested the previously tested chromoproteins against the newly pipetted chromoproteins to see if the temperature change would occur at a different temperature once a chromoprotein has already been heated. We placed these chromoproteins into a 40 °C oven and raised the temperature by a degree C over 6 minutes up to 60 °C. The chromoproteins all lost their color again and lost their color at the same temperature as before and compared to the already once heat tested chromoproteins. We then again rehydrated all 12 chromoproteins with 3 µL of milliQ water and the color came back. This test shows a reversible color change for all 12 chromoproteins at lower temperatures than seen in cell lysate tests and also shows this heat testing can be done multiple times with consistent results. Because of the range of temperatures the chromoproteins lose color at there is the application for a paper base thermometer. The temperature results were slightly different for the 4 chromoproteins we had previously tested most likely because the 4 chromoproteins had been sitting longer on the bench top after purification than the other 8 chromoproteins.
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<figcaption>Figure 22: 12 chromoproteins on the cellulose sheet before heat is added. PrancerPurple (left), CupidPink, TinselPurple, VixenPurple, MaccabeePurple, SeraphinaPink, LeorOrange, ScroogeOrange, BlitzenBlue, DreidelTeal, DonnerMagenta, VirginiaViolet.</figcaption></figure>
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<figcaption>Figure 23: 12 chromoproteins after being heated to 60 °C. All lost color. </figcaption></figure>
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<figcaption>Figure 24: 12 chromoproteins after being rehydrated. Color regained. </figcaption></figure>
In the interest of moving towards a biologically based paper thermometer, we also did a Gibson Assembly to add a cellulose binding domain to the end of our chromoprotein. This was first done successfully with AE Blue from the iGEM registry. Once this construct was successfully transformed and expressed in bacteria, the protein was extracted and dialyzed. The concentrated protein was then pipetted onto cellulose sheets and underwent a series of heat tests. It was found that, while this protein initially appeared blue (Figure 25), it begins to turn purple at 55 °C (Figure 26) and this purple color becomes more pronounced as temperature is increased (Figure 27). Interestingly, when allowed to cool back to room temperature, the blue color returned (Figure 28).
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<figcaption>Figure 25</figcaption></figure>
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<figcaption>Figure 26</figcaption></figure>
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<figcaption>Figure 27</figcaption></figure>
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<figcaption>Figure 28</figcaption></figure>
We then created NASA sticker using the AE blue fusion protein to coat a cellulose sheet as the blue background of the NASA logo and added the lettering and red swoosh with stickers. This sticker was then fixed to a glass container using double sided tape. Hot water was added to the glass container and after 1 minute of exposure to heat, the AE blue-CBD fusion protein turned purple (Video 1). Cold water was then added to the glass container and the AE blue-CBD fusion protein returned to its original blue color (Video 2). This testing shows a reversible, color changing, temperature sensitive fusion protein and is the prototype of a biologically based paper thermometer.
<figure><video src="https://static.igem.org/mediawiki/2016/c/cb/T--Stanford-Brown--CP-44-real.mp4" type="video/mp4" class="vid" controls="true"/></figure>
<figure><video src="https://static.igem.org/mediawiki/2016/9/9e/T--Stanford-Brown--CP-45.mp4" type="video/mp4" class="vid" controls="true"/></figure>
We also added a cellulose binding domain to the DNA2.0 chromoproteins using Gibson assembly. The sequence for these proteins were transformed into bacteria, expressed, extracted, and fix to cellulose sheets. Figure 29 shows the 2 cellulose binding domain chromoproteins (PrancerPurple and LeorOrange) on cellulose sheets. After being allowed to set for three days, we tested the binding capabilities of the cellulose binding domain by washing the cellulose sheet the chromoproteins were bound to with a steady stream of water for 1 minute. After this washing, no color change was detected, indicating that the cellulose binding domain was effective at fixing the chromoproteins to the sheet (Figure 30).
<figure class="fig"><img src="" class="img-L"> <figcaption>Figure 29: Before cellulose binding domain testing. PrancerPurple-cellulose binding domain (top) and LeorOrange-cellulose binding domain (bottom. </figcaption></figure>
<figure class="fig"><img src="" class="img-L"> <figcaption>Figure 30: After cellulose binding domain testing. PrancerPurple-cellulose binding domain (top) and LeorOrange-cellulose binding domain (bottom).</figcaption></figure>
<a name="highlight3"></a>Testing the prototype
In collaboration with the <a href=http://stanfordssi.org/teams/balloons>Stanford High Altitude Ballooning Team</a>, we field tested our AE Blue-CBD fusion protein at a high altitude. This AE Blue-CBD fusion protein was extracted from the cells that were expressing it and purified using dialysis to ensure that only the fusion protein remained for this experiment. Prior to the flight we obtained permission from the US Environmental Protection Agency and iGEM HQ. It is important to note that nothing living was sent into the environment to be tested and that our sample was recovered. No environmental contamination occurred as a result of this experiment.
Using our extracted fusion protein, we plated 20 µL drops onto a cellulose sheet that had had wax wells printed onto it (Figure 31). Every well seen in this image is from the same chromoprotein. This chromoprotein is the same as was seen earlier in the NASA logo heat test. Because there are higher levels of UV radiation in the atmosphere than are in our lab environment, we used UV-opaque and UV-transparent glass to cover the top and bottom row of the grid. The center row was left exposed to the elements as a control. These were then mounted onto the payload of the Stanford High Altitude Balloon Team’s balloon (Details in Figures 32, 33, and 34) and were readied for launch!
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<figcaption>Figure 31</figcaption></figure>
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<figcaption>Figure 32</figcaption></figure>
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<figcaption>Figure 33</figcaption></figure>
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<figcaption>Figure 34</figcaption></figure>
A GoPro was mounted on the payload as well in order to catch inflight data. In the image to the right, taken at 10000 feet from the surface, the chromoproteins can be seen starting to change their color from blue to purple (Figure 35). A tracking device placed on the balloon allowed for the payload to be recovered once the balloon had burst. The image below was taken of the fusion proteins immediately after payload recovery (Figure 36). As can be seen, the once-blue fusion proteins are now purple. This purple color was persistent for six hours before eventually returning back to blue which is unlike previous heat tests in that usually the blue color comes back rather quickly.
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<figcaption>Figure 35</figcaption></figure>
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<figcaption>Figure 36</figcaption></figure>
This could have occurred for a variety of reasons. The simplest explanation is that the exposure time to heat stress was much longer in the field test than in the lab. Usually our heat test experiments last anywhere from 5 to 30 minutes of constant heat exposure. As a result, it might be easier for the chromoproteins to regain their structure afterwards. Because all three of the levels of UV-exposure that were tested had the same degree of color change, it seems unlikely that the exposure to UV was responsible for the prolonged color change we witnessed. However, it is possible that even the UV-resistant glasses we used were not enough to block out trace amounts of UV and that these trace amounts of UV destabilized the structure of the chromoproteins in such a way that the prolonged color change occurred. Below is a video capturing the flight (Video 3).
<figure ><video src="https://static.igem.org/mediawiki/2016/8/81/T--Stanford-Brown--SB_SSI_ChromoproteinLaunch.mp4" type="video/mp4" class="vid" controls="true"/></figure>
References
- Schlatter, Thomas W. "Atmospheric Composition and Vertical Structure." National Oceanic and Atmospheric Administration (2009): n. pag. Web.
- Shkrob, Maria A., Yurii G. Yanushevich, Dmitriy M. Chudakov, Nadya G. Gurskaya, Yulii A. Labas, Sergey Y. Poponov, Nikolay N. Mudrik, Sergey Lukyanov, and Konstantin A. Lukyanov. "Far-red Fluorescent Proteins Evolved from a Blue Chromoprotein from Actinia Equina." Biochem. J. Biochemical Journal 392.3 (2005): 649-54. Web.
- Langan, P.s., D.w. Close, L. Coates, R.c. Rocha, K. Ghosh, C. Kiss, G. Waldo, J. Freyer, A. Kovalevsky, and A.r.m. Bradbury. "Corrigendum to “Evolution and Characterization of a New Reversibly Photoswitching Chromogenic Protein, Dathail” [J. Mol. Biol., 428, (2016), 1776–89]." Journal of Molecular Biology 428.20 (2016): 4244. Web.
- "Lumio Green Detection Kit - Thermo Fisher Scientific."; N.p., n.d. Web. 2 Oct. 2016.
- "FLAG Tag Peptide|Versatile Fusion Tag|CAS# 98849-88-8." FLAG Tag Peptide|Versatile Fusion Tag|CAS# 98849-88-8. N.p., n.d. Web. 02 Oct. 2016.
- Carrard, G., A. Koivula, H. Soderlund, and P. Beguin. "Cellulose-binding Domains Promote Hydrolysis of Different Sites on Crystalline Cellulose." Proceedings of the National Academy of Sciences 97.19 (2000): 10342-0347. Web.
</html> Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12INCOMPATIBLE WITH RFC[12]Illegal NheI site found at 7
Illegal NheI site found at 30 - 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000INCOMPATIBLE WITH RFC[1000]Illegal BsaI.rc site found at 740
References
None |