Latest revision as of 06:01, 12 October 2023

IsPETase-Linker-CBM4-6xHisTag

The hydrophobicity of the PET surface prevents IsPETase from binding to PET, which prevents IsPETase from functioning well. By adding the hydrophobic domain CBM4 to IsPETase, the hydrophobic domain of IsPETase can bind to the hydrophobic surface of PET more easily under the force of water molecule movement.

Construction

A recombinant plasmid containing this complex element was constructed using pET-22b(+) as a vector. The recombinant plasmid was obtained by fusing IsPETase with CBM4, a hydrophobic domain with a linker, using the Gibson assembly method. The recombinant plasmid was transformed into an E.coli BL21(DE3) sensory state. Colony PCR was performed using T7 and the post primer of the amplified domain as primers as shown in Fig.1.

Fig.1 Colony PCR bands of pET22b-IsPETase-CBM4

6-9: pET22b-IsPETase-linker-CBM4

Characterization

1. SDS-PAGE

After the protein was induced by 1 mM IPTG, we used a nickel column to purify the protein because CBM4 incorporates 6xHis Tag. After the column was equilibrated, 30 mM and 300 mM imidazole buffer were added to rinse the column, and the target protein eluted with 300 mM imidazole buffer was collected. After purification, SDS-PAGE was performed to confirm the successful expression, as shown in Fig.2.

Fig.2 SDS-PAGE of IsPETase-CBM4 supernatant, starch, and purified protein after the introduction of the molecular chaperone pGro7.

M:180kDa Prestained Protein Marker

4-6:IsPETase-CBM4 supernatant, precipitate, and purified enzyme solution (protein size~46kDa)

2. HPLC

After protein purification, an enzymatic reaction was performed to measure the enzyme activity. The substrate used was PET powder, which was decomposed into TPA and MHET by IsPETase, and the reaction solution was subjected to high performance liquid chromatography (HPLC), and the 6-min liquid phase result corresponded to TPA and the 8-min liquid phase result corresponded to MHET. The peak area of the product output from the liquid chromatograph was converted into the concentration of the product through a standardized line, as shown in Fig.3.

Fig.3 Concentrations of TPA and MHET products of 500 nM IsPETase-CBM4 reacted with PET powder for 48 h at different temperatures. (A) is the product concentration at 30°C, (B) is the product concentration at 37°C, and (C) is the product concentration at 45°C. The product concentration was determined by the reaction of 500 nM IsPETase- CBM4 with PET powder for 48 h at different temperatures.

Conclution

At 30°C, the degradation of PET by IsPETase-CBM4 was significantly reduced compared with that by WT. At 37°C, the effect of IsPETase-CBM4 on PET degradation decreased compared with that of WT. At 45°C, the effect of IsPETase-CBM4 on PET degradation was significantly increased compared with that of WT, which was about 4 times that of WT. This suggests that CBM4 may enhance the hydrophobicity of the enzyme as well as the high temperature resistance of the enzyme.

Sequence and Features