Revision as of 02:22, 1 September 2023

T7-RBS-SpyTag-GFP-SpyCatcher-Tr

THERMOSTABILITY OF WILD-TYPE GFP

The BioBrick pT7-eGFP (Part:BBa_K1833000) comprises a T7 promoter, RBS, and terminator, with an inserted gene of GFPmut3b. This plasmid was retransformed into E. coli BL21. Upon 0.3 mM IPTG induction at 25°C for 20 hrs, bacterial lysates underwent heat tests at varied temperatures for 3 minutes, as indicated in Figure 1. Relative to the untreated control, fluorescence fold change depicted thermostability trends from 70°C, 80°C, to 90°C, retaining 59%, 12%, and 1% of the GFP signal, respectively. This data provided insights into the innate heat tolerance properties of GFPmut3b protein.

Figure 1. Thermostability of GFPmut3b protein. E. coli BL21 transformed with BBa_K1833000 was induced using 0.3 mM IPTG at 25°C for 20 hrs. Bacterial lysates were subjected to temperatures of 70°C, 80°C, and 90°C for 3 min each. Subsequently, the fluorescence of 100μl from each treated lysate was measured at Ex/Em = 483/513 nm. All values were normalized to the average of the untreated control, with the resulting ratio representing the fluorescence fold change.

THERMOSTABLE CYCLIZED SPYTAG-GPF-SPYCATCHER

PLASMID CONSTRUCTION

To enhance the thermostability of the GFP protein, we deleted start (ATG) codon and stop (TAA) codon, and incorporated SpyTag at the N-terminus and SpyCatcher at the C-terminus. This DNA fragment was synthesized by Integrated DNA Technologies, Inc. (IDT) and then cloned into pSB1C3 (SpyTag-GFP-SpyCatcher, Basic Part:BBa_K4652000). Then, the part was connected with a T7 promoter (Part:BBa_K1833999), a strong RBS (Part:BBa_B0030), and a double terminator (Part:BBa_B0015). This setup mirrored the context of pT7-eGFP (Part: BBa_K1833000), with the exception of the added SpyTag and SpyCatcher. The final construct was verified using colony PCR (Figure 2) and further validated through DNA sequencing. This resultant construct was designated as the improved BioBrick part, pT7-SpyTag-GFP-SpyCatcher (Composite Part: BBa_K4652002).

Figure 2. Comparison of wild-type GFPmut3b and cyclized SpyTag-GPTmut3b-SypCatcher proteins. E. coli BL21 transformed with indicated plasmid was induced using 0.3 mM IPTG for 25°C for 20 hrs. Bacterial lysates were subjected to temperatures of 90°C for 3 min. The fluorescence of 100μl lysates was measured at Ex/Em = 483/513 nm. All values were normalized to the average of the untreated control, with the resulting ratio representing the fluorescence fold change.

REFERENCE

1. Schoene C, Bennett SP, Howarth M. SpyRings Declassified: A Blueprint for Using Isopeptide-Mediated Cyclization to Enhance Enzyme Thermal Resilience. Methods Enzymol. 2016;580:149-67. doi: 10.1016/bs.mie.2016.05.004. Epub 2016 Jun 16. PMID: 27586332.

Sequence and Features