Part:BBa_K5034227
Pi <-> PolyP
Contents
Basic Description
This basic part encodes the PPK2 gene which is initially from Pseudomonas aeruginosa and we performed codon optimization on, is expressed in the PYYDT plasmid. The PPK2 enzyme facilitates the reversible conversion between inorganic polyphosphate (PolyP) and inorganic phosphate (Pi), playing a crucial role in phosphate metabolism. It distinguished from PPK1 by the following: synthesis of poly P from GTP or ATP, a preference for Mn2+ over Mg2+, and a stimulation by Poly P. The reverse reaction, a poly P-driven nucleoside diphosphate kinase synthesis of GTP from GDP, is 75-fold greater than the forward reaction, Poly P synthesis from GTP.
Figure 1: Basic function of PPK2
Sequence and Features
- 10INCOMPATIBLE WITH RFC[10]Illegal prefix found in sequence at 4981
Illegal suffix found in sequence at 1 - 12INCOMPATIBLE WITH RFC[12]Illegal EcoRI site found at 4981
Illegal SpeI site found at 2
Illegal PstI site found at 16
Illegal NotI site found at 9
Illegal NotI site found at 2834
Illegal NotI site found at 4987 - 21INCOMPATIBLE WITH RFC[21]Illegal EcoRI site found at 4981
Illegal BglII site found at 3580 - 23INCOMPATIBLE WITH RFC[23]Illegal prefix found in sequence at 4981
Illegal suffix found in sequence at 2 - 25INCOMPATIBLE WITH RFC[25]Illegal prefix found in sequence at 4981
Illegal XbaI site found at 4996
Illegal SpeI site found at 2
Illegal PstI site found at 16
Illegal NgoMIV site found at 562
Illegal NgoMIV site found at 4244
Illegal NgoMIV site found at 4527
Illegal AgeI site found at 402 - 1000COMPATIBLE WITH RFC[1000]
Chassis and Genetic Context
Successfully expressed in Escherichia coli DH5α and BL21(DE3) strains.
Construct features
Promoter: Constitutive promoter for continuous expression. We use tac promoter in our experiment.
RBS: Strong ribosome binding site for efficient translation. We use BBa-B0034 which shows the strongest translation in our experiment.
PPK2 Coding Sequence: Encodes the polyphosphate kinase 2 enzyme.
Terminator: Efficient transcription terminator to ensure proper mRNA processing. We use a double terminator rrnBT1-T7TE(BBa_B0015) in our experiment.
Figure 2: PCR of target genes before plasmids construction (The extra small fragment in the picture is primer dimer)
Figure 3: Basic construction of PPK2 plasmid
Figure 4: Construction of PPK2 plasmid
Figure 5: Bacterial PCR indicating that different plasmids can replicate in Shewanella
Origin (Organism)
PPK2 Gene Source: Pseudomonas aeruginosa PAO1 strain.
Plasmid Backbone: pBBR1MCS plasmid, a standard vector used for gene expression in synthetic biology. The plasmid backbone(BBa_K5034201) of this part is a modified version of pBBR1MCS, with a double terminator(BBa_B0015) on it.
Experimental Characterization and results
In our team’s previous research we found that the behavior of the modified Shewanella did not reach our expectation and the electron microscopic observation also showed an abnormal morphology of the bacterium, we postulated that too much PPK1 may lead to an abnormal charge distribution in the bacterium thus result in a decrease in the bacterium's activity and a reduction in its capacity for electricity production, so we planed to improve the situation by introducing different polyphosphate hydrolases which influence the phosphorus metabolism of Shewanella.
Electricity production: Using half-cell reaction(electrochemistry) to measure the electricity production ability.
Capacity to polymerize phosphorus: Conducting molybdate assays to determine Pi concentration.
The expression of hydrolase PPK2 showed relatively high phosphorus accumulation and electricity generation ability. Also, the ATP level is considerably enhanced.
Figure 6: Statistical data on electricity production capacity of Shewanella with the introduction of different hydrolases
Figure 7: statistical data on the phosphorus accumulation capacity of Shewanella with PPK2
Figure 8: ATP level in Shewanella with the introduction of different hydrolases
Potential Applications
Managing phosphate levels in contaminated environments;
Enhancing phosphate metabolism in engineered microbial systems;
Optimizing phosphate utilization in industrial microbial processes.
Enhancing the performance of bioelectrochemical systems for electricity generation in providing a renewable and sustainable source of electricity, reducing reliance on fossil fuels and contributing to cleaner energy production.
References
1.Zhang, H., Ishige, K., & Kornberg, A. (2002). A polyphosphate kinase (PPK2) widely conserved in bacteria. Proceedings of the National Academy of Sciences, 99(26), 16678-16683. 2. Neville, N., Roberge, N., & Jia, Z. (2022). Polyphosphate Kinase 2 (PPK2) enzymes: Structure, function, and roles in bacterial physiology and virulence. International Journal of Molecular Sciences, 23(2), 670. 3. Itoh, H., & Shiba, T. (2004). Polyphosphate synthetic activity of polyphosphate:AMP phosphotransferase in Acinetobacter johnsonii 210A. Journal of Bacteriology, 186(15), 5178-5181.
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