Part:BBa_K2916043

Expression of RRF in E.coli

This part is used for expression of Ribosome Recycling Factor (RRF) needed for the OnePot PURE cell-free system.

Usage and Biology

The Ribosome Recycling factor is a part, along with the Release Factors, of the Termination phase of the protein biosynthesis. Its function is to recycle the ribosomes after the completion of protein synthesis.

In our project we used RRF as a part of the protein solution needed for OnePot PURE cell-free system produced with the method of gravity flow affinity chromatography, as described in the protocol we designed.

Expression and purification of RRF

RRF is one of the proteins we used for the OnePot PURE cell-free system. We expressed it in M15 E.coli strain using a pQE60 vector. The expression system has a T5 lac operator, RBS and a lambda t0 Terminator, enabling us to regulate the expression with IPTG.

Methods

RRF was purified using our protocol . To test if the protein was actually expressed, we performed a SDS-PAGE that is presented below. On the left side we can see the results included in the initial OnePot PURE paper (Lavickova et al, 2019) while on the right (batch1_a,b and batch2_a,b) are the solutions we produced ourselves. (The procedure we followed and the conditions of the experiment can be found here).

Figure 1: SDS-PAGE of OnePot PURE protein solution.

Conclusion
RRF has a molecular weight of around 22kDa, but even though we cannot be absolutely sure if the band shown is only due to it, we may assume that it is expressed. To verify the existence and functionality of this protein we need to proceed with more experiments that would be mainly focused on the efficiency of the system.

OnePot PURE functionality test

To make sure that we have all the proteins in our OnePot PURE protein solution, and that they all function properly we need check if proteins can be expressed in our OnePot PURE cell-free system.

Methods

We expressed superfolding GFP following the protocol we designed in 10μl reactions, and measured the fluorescence on a plate reader at excitation wavelength of 535nm. We tested the expression using different concentrations of the sf GFP DNA template and also compared it with the fluorescence produced in PURExpress from NEB.

Figure 2: sf GFP expression using 10nM DNA template.

Figure 3: sf GFP expression using 5nM DNA template.

Figure 4: sf GFP expression using 2.5nM DNA template.

Figure 5: Comparison between OnePot PURE and PURExpress at saturation.

Conclusion
The expression was successful so we can confirm that RRF exists in our protein solution and is also functioning properly.

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  COMPATIBLE WITH RFC[1000]