Difference between revisions of "Part:BBa K5531011"

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pET-Dual-HisPPG-P15VP4-P4H

Sequence and Features

BBa_K5531011 (pET-Dual-HisPPG-P15VP4-P4H)

Construction Design

This targeted gene, PKG50-P4VP4 (BBa_K5531003), synthesized by a biotech company, contains a proline-free heterotrimeric collagen-like protein motif PKG fused with the P15VP4 protein. Meanwhile, P4H (BBa_K5531012) is also co-expressed in this plasmid due to the lack of proline hydroxylation-modifying enzymes (prolyl 4-hydroxylases (P4H)) in procaryotes, which is essential for collagen stability. The pET-Dual-N-His-TEV (BBa_K5531006) serves as the vector. The homologous recombination method was employed to construct pET-Dual-HisPPG-P15VP4-P4H (BBa_K5531011).

Fig. 1. Plasmid map of pET-Dual-HisPPG-P15VP4-P4H

Experimental Approach

We isolated pET-Dual-N-His-TEV vectors from bacterial solutions primarily by centrifugation. The vectors were then obtained from the remains in the absorption column. Subsequently, we linearized the vectors using restriction enzymes and conducted electrophoresis to analyze the products. The electrophoresis result displayed consistency toward the expected outcome (HisPPG-P15VP4 is 2000 bp, and P4H is 630 bp), indicating success in pET-Dual-HisPPG-P15VP4-P4H construction. We selected colonies and sent them directly for sequencing. Figure 2 shows the success of pET-Dual-HisPPG-P15VP4-P4H construction.

Fig. 2. The results of pET-Dual-HisPPG-P15VP4-P4H

Characterization/Measurement

Later, the plasmid mounted with the gene of PPG-P15VP4 was transferred to E. coli DH5α to replicate. The extracted plasmid was transferred into E. coli BL21, which can help express His-PPG-P15VP4. After the colony PCR of E. coli BL21 was finished and verified, the bacteria were cultured and treated with 0.2 mM IPTG, which can promote protein expression. After promoting the protein expression overnight, the protein was purified via His-tag Purification Resin and went through SDS-PAGE electrophoresis and Native-PAGE electrophoresis. The target protein PPG-P15VP4 has a size of 59 kDa.

Fig. 3. The expression of PPG-P15VP4 using E. coli BL21.

Collagen of the C-D-E-VP4 complex (in a 1:1:1 ratio) was diluted to a concentration of 0.5 mg/mL and incubated at 37°C for 1 hour before undergoing native-PAGE and SEC analysis. As illustrated in Figure 4, the samples were divided into two distinct clusters: high-molecular-weight and low-molecular-weight states. Each cluster contained multiple bands, indicative of varying degrees of proline hydroxylation. Based on the construct design, we hypothesized that the high-molecular-weight clusters represented the trimer assemblies, while the low-molecular-weight clusters corresponded to the monomers. This hypothesis was confirmed by the SEC analysis, as depicted in Figure 4. The peaks for collagen-VP4 B ranged from 0.5 to 0.8 CV, with the prominent peaks at 0.56 CV and 0.66 CV, respectively, suggesting the presence of trimer and monomer macromolecules.

Fig. 4. Native-PAGE analysis (left) of oligomeric states of collagen C-D-E complex; Size exclusion chromatographic (SEC) analysis (right) of oligomeric states of collagen C-D-E complex.

References

[1] Gauba V, Hartgerink JD. Self-assembled heterotrimeric collagen triple helices directed through electrostatic interactions. J Am Chem Soc. 2007 Mar 7;129(9):2683-90.
[2] Liu Zezhong; Zhou Jie; Zhu Yun; Lu Lu; Jiang Shibo; School of Basic Medical Sciences, Fudan University; Department of Pharmacology, School of Pharmacy, Fudan University; Institute of Biophysics, Chinese Academy of Sciences.