Part:BBa_K1582001
sJanus from Trichoderma reesei
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25INCOMPATIBLE WITH RFC[25]Illegal NgoMIV site found at 187
- 1000INCOMPATIBLE WITH RFC[1000]Illegal SapI site found at 196
Usage
Janus is a kind of amphipathic protein which could self-assembly spontaneously. Due to its special properties, we could make many new applications. We use them as substrate to fix antibodies on a high-flux tumor detection chip. Meanwhile, they are used to catch cutinases for plastic degradation. We even make them into a fusion to test if the enhancement could be better. And we use its amphipathicity to achieve protein separation, where they act as a special purification tag, and the system could be as simple as polymer, detergent and water.
Biology
Janus could be produced by filamentous fungi, such as Ascomycetes and Basidiomycetes, and their scientific name is hydrophobin. Many different aspects of fungal development have been attributed to Janus. For example, they are thought to play a role in the formation of aerial hyphae and fruiting bodies. One of the most important features of Janus is that they are able to assemble spontaneously into amphipathic monolayers at hydrophobic–hydrophilic interfaces.
There are two classes of Janus, which are divided by the stability of their self-assembly. sJanus from Trichoderma reesei belongs to Class II. The assemblies of class II Janus can be dissolved in ethanol or sodium dodecyl sulfate or through the application of pressure or lowering of the temperature.
Protein Expression
The bacteria ( E.coli BL21) were cultured in 5mL LB liquid in 37℃ for 6-8 hours. The antibiotic we used in inJanus-m and sJanus-m is kanamycin, and for sJanus is ampicillin. Then we used 500μM IPTG to induce in 37℃ for 4h.
Figure 1. Pre-expression. We successfully expressed sJanus, sJanus-m and inJanus-m.
Expression condition:
1. Mix the supernatant after centrifugation with the GST medium and incubate them in the shaker for 1~2h.
2. Add the intermixture to the column. Collect the flow-through and add it to the column again. (You can repeat the procedure for 2~3 times if necessary.)
3. Wash the column by 20ml 1xPBS for three times (more if necessary).
4. Add Prescission Protease to the column (the mass ratio of PP and your protein is 1:10). Then incubate them in the shaker overnight.
5. Collect the flow-through which is your sample. Purify your product by using UPLC.
6. Wash the column by GSH and recover the column.
Super Protein Chip
Results
1. The optimal concentration of inJanus is 200μg/ml.
2. The optimal concentration of antigens (CEA, AFP and CA15-3) is 2.5μg/ml.
3. The optimal concentration of antibodies is 5μg/ml.
Figure 4.Hydrophobins sJanus show good effects of antibodies fixing. Here we use antibodies with green fluorescence tag as example. The spots with strong fluorescence represent successful binding between capture antibody (probe) and antigen (tumor marker).
Figure 5.Hydrophobins inJanus tend to show weak fluorescence signal. After compared experiments, we discovered that increasing the incubation time helps to improving detecting sensitivity.
Project Achievements
1.We introduced a new method of protein chip substrate modification by using Janus, and verified its feasibility.
2.We confirmed the optimal concentration of antigens and antibodies in the detection of tumor markers, which helps to save materials to the most extent and keep the reliability of the results at the same time.
3.The experiments were conducted with different kinds of antigens and antibodies, ensuring the universality of the tumor detection chip under a certain range.
Optimization
1.In the beginning, due to our inexperience, the concentration of antigens and antibodies was too high, which leads to excessive strong fluorescence signal intensity.
At first we thought it was caused by the improperly operation of microscope, but after literature reviewing and analyzing, we tried lowering the concentration about four times and achieved good results.
Figure 6.Here is the excessive strong fluorescence signal intensity caused by high concentration.
Figure 7.Good results were achieved after lowering the concentration.
2. In mid-stage, many crystallized structures appeared in the protein spot, and hence influenced the image quality and observation results. To solve this problem, we consulted large quantities of data and information, and discovered a similar case arising when solutions of antibodies and antigens were stored for too long, leading to degeneration. So we reformulated all the solutions we need, and crystallization disappeared. From this we learned that reagents should be used right after they were ready. In this case, another possible cause was that we used TBST in the last washing step, which may also lead to crystallization. In the upper course of experiments we used water instead of TBST.
Figure 8.Crystallized structures appeared.
Figure 9.Crystallized structures disappeared after reformulating all the solutions we need.
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