Difference between revisions of "Part:BBa K2906000"

Revision as of 17:06, 20 October 2019

sfGFP with Tet Promoter

This is an improved part of BBa_I746909. By adding a Tet promoter, we are ensuring that sfGFP is tightly controlled, and expressing a higher level of fluorescence in the initial hours after induction MediaWiki

Superfolder GFP also known as sfGFP is a GFP-derived green fluorescent protein. (Pédelacq et al., 2006). GFP is a protein isolated from the jellyfish Aequorea Victoria that exhibits green fluorescence when exposed to light in the blue to the ultraviolet range (Prendergast and Mann, 1978; Tsien, 1998). A series of mutations performed by Pédelacq et al. obtained a GFP variant able to rapidly fold and mature. This ultimately also lead to enhanced fluorescence intensity (Frenzel et al., 2018). This composite part is made of sfGFP (BBa_K1321337) expressed by a Tet promoter (BBa_R0040). The protein is able to express colour and auto secrets to the media.

Characterisation:

To show whether this part worked, we decided to measure fluorescence, normalised by OD. Optical Density values were measured at 600 nm. We grew the cells to an OD600 of ~0.6 and induced them with 100 nM of anhydrotetracycline. Then, they were loaded in triplicates into a 96-well plate and left overnight. For OD values, the blank was LB media, and for RFU the blank was E. coli TOP10 since it does not express any colour. The values were individually normalised by dividing RFU/OD and then averaged to plot the mean against time. An RFU value of 0 corresponds to baseline E. coli TOP10 measurements.

Figure 1. The plot shows the mean RFU/OD from three replicates of each construct expressed in E. coli DH5⍺ and BL21(DE3). The OD was measured at 600 nm and GFP fluorescence was measured at Ex ƛ 485, Em ƛ 510, every 15 minutes for 13 hours. The RFU values were normalised by the OD and the triplicates averaged. All values have been blank-corrected. A total of 52 recordings were made per well, with three wells per construct. 'Colour Alone' represents this part, pTet + sfGFP. The values suggest that sfGFP is expressed at very high levels in both DH5a and BL21(DE3).

SDS

ONGOING

Qualitative Data:

This is an essential new part, as sfGFP is a very common reporter gene. Additionally, we show in our wiki [1] how this is an improved part over the sfGFP provided by iGEM with a T7 promoter. We hope that this new part can be useful for future teams!

References:

Frenzel, E., Legebeke, J., Van Stralen, A., Van Kranenburg, R. and Kuipers, O. P. (2018) ‘In vivo selection of sfGFP variants with improved and reliable functionality in industrially important thermophilic bacteria’, Biotechnology for Biofuels. BioMed Central Ltd., 11(1). doi: 10.1186/s13068-017-1008-5.

Pédelacq, J. D., Cabantous, S., Tran, T., Terwilliger, T. C. and Waldo, G. S. (2006) ‘Engineering and characterization of a superfolder green fluorescent protein’, Nature Biotechnology, 24(1), pp. 79–88. doi: 10.1038/nbt1172.

Prendergast, F. G. and Mann, K. G. (1978) ‘Chemical and Physical Properties of Aequorin and the Green Fluorescent Protein Isolated from Aequorea forskålea†’, Biochemistry, 17(17), pp. 3448–3453. doi: 10.1021/bi00610a004.

Tsien, R. Y. (1998) ‘THE GREEN FLUORESCENT PROTEIN’, Annual Review of Biochemistry. Annual Reviews, 67(1), pp. 509–544. doi: 10.1146/annurev.biochem.67.1.509.

Sequence and Features