Part:BBa_K921000
T7 RNAP + IPTG->PoPs (Mutant I)
This is a mutant T7 promoter that includes a lacO operator site. The promoter is inhibited by the LacI protein and can be induced by IPTG. The promoter sits in the 5' region of a gene and initiates transcription when cells express T7 RNA polymerase. Please use cell strains that are compatible with T7 expression vectors.
The following parameters were calculated and compared against the "wild-type" promoter
| Promoter | BBa K921000 | BBa K921001 | BBa K921002 |
|---|---|---|---|
| Transcription Strength | 97% | 72% | 127% |
| Translational Efficiency | 6% | 6% | 94% |
Cells were grown in M9 media without casamino acids. Fluorescence intensities were normalized to optical density (absorbance @600nm).
Fluorogen-activating proteins were used as protein reporters in our characterization experiment (see details in here). Here, 10uM malachite green was added to each well of a 96-well plate and fluorescence intensities were recorded over time. Our model was used to simulate the time lapse data using differential equations.
The Spinach aptamer was used as a RNA reporter in our characterization experiment (see details in here). 200uM DFHBI was added to each well of a 96- well plate and fluorescence intensities were recorded over time. Our model was used to simulate the time lapse data using differential equations.
Note: To learn more about how we characterized this set of promoters, click here.
Discussion:
Mutant I of this set of T7/lac promoters produces a lot of protein and seems to respond efficiently to the addition of IPTG. The design of this mutant was based on random mutations throughout the promoter including the recognition site, initiation site and the lac operator. This promoter was expected to have a lower affinity to the T7 RNAP and therefore have a lower amount of protein expression. We hypothesize that the large amount of protein product is due to the lower affinity to the T7 RNAP allows the polymerase to move along the DNA to start initiation more frequently.
It is important to note that across all three promoters, multiple dips were recorded in the readings even though our data is normalized against optical density to take into account viable cell number. This is due to the fact that strong promoters cause selective pressure and multiphasic growth curves. This can cause sinusoidal behavior in gene expression. The approximate frequency of protein production across all three promoters is 1 hour-1.
Usage and Biology
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000COMPATIBLE WITH RFC[1000]
Functional Parameters
| direction | Forward |
| efficiency | 169% |
| negative_regulators | LacI (Hypothesized LacIQ compatible) |
//function/regulation/transcriptional
//plasmid/expression/t7
//promoter
//regulation/negative
| direction | Forward |
| efficiency | 169% |
| negative_regulators | LacI (Hypothesized LacIQ compatible) |