Difference between revisions of "Part:BBa K2680550"

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deGFP-ssra

de-GFP ssra is a destabilized GFP created by "fusing amino acids 422–461 of the degradation domain of mouse ornithine decarboxylase (MODC) to the C-terminal end of an enhanced variant of GFP (EGFP) ¹ This destabilized GFP is fitted with an ssrA degradation tag.

References

1. Li‡, X., Zhao, X., Fang, Y., Jiang, X., Duong, T., & Huang, C. F. (1998, December 25). Xianqiang Li. Retrieved from http://www.jbc.org/content/273/52/34970.full.html

Sequence and Features

Contribution by Team ZJUT-China 2021

Group: Team ZJUT-China 2021
Author: Lianjie Sha and Xia Yao
Summary: According to the lectures, we learned that the degradation rate of eGFP-ssrA could be measured. In cell-free system, protein degradation by clpXP is described by a zeroth order chemical kinetic,and clpxp protein can recognize the protein with ssrA tag, so it is useful to add clpxp degrading the degfp. This year,on the basis work of iGEM18_William_and_Mary, ZJUT-China measured the different eGFP degradation rate by adding different concentrate of plasmid P70-clpxp (Part:BBa_K3885203) based on the reference. We hope it will support more help on modelling and further experiments.

Methodology

There are two methods to express clpxp protein: co-expression and pre-expression.Accelerated protein degradation can be achieved by co-expression of P70a-ClpXP, by adding protein to a cell-free system pre-incubated with P70a-ClpXP for an hour or by adding dilutions of pre-expressed clpXP (P70a-clpXP, 3nM). Different methods can provide different rates of protein degradation, ranging from 9.3 nM/min to 250 nM/min. By expressing clpXP, protein synthesis can be adjusted to an appropriate rate.[1]

Results

Group1: Pre-expression for an hour

ClpXP [nM]	eGFP degradation rate [nM/min]
0	6.51±1.25
0.2	28.04±3.87
0.4	48.24±8.06
1	88.32±17.71
2	159.13±21.92
6	256.07±38.24

ClpXP [nM]	eGFP degradation rate [nM/min]
0	9.3
0.2	29.4
0.4	47.3
1	80.1
2	128.9
6	128.4

Degradation rate of deGFP upon different expression methods of clpXP. The degradation rate of deGFP-ssra only using the endogenous clpXP has been determined by an assay, which is achieved by measuring the kinetics after adding pure His-GFP-ssrA (5μM) to the cell-free system.

Analysis

As shown in the figure above, the higher the concentration of CLPXP, the faster the degradation of eGFP-ssrA. Meanwhile, according to the table, when ClpXP with the same concentration was added, eGFP degradation rate in pre-expression was from 6.5 nM/min to 256 nM/min, while in co-expression, eGFP degradation rate was from 9.3 nM/min to 128 nM/min. It can be concluded that pre-expression is more conducive to eGFP protein degradation than co-expression.

Reference

[1] Garamella J, Marshall R, Rustad M, et al. The all E. coli TX-TL toolbox 2.0: a platform for cell-free synthetic biology[J]. ACS synthetic biology, 2016, 5(4): 344-355.