Part:BBa_K5034216
PolyP <->Pi
This part is activated by an efficient promoter.It can reversibly convert Poly p and Pi. This reversible process favors the generation of Poly P.For the first time, we expressed this element in a strain of Shewanella and conducted codon optimization based on Shewanella.
Basic Description: This basic part encodes the PPK1 gene which is initially from Citrobacter freundii and we performed codon optimization on, is expressed in the PYYDT plasmid. This basic part is designed to facilitate the reversible conversion between inorganic polyphosphate (PolyP) and inorganic phosphate (Pi). The PPK1 enzyme is known for its ability to synthesize PolyP from ATP and to degrade PolyP back to Pi, with a preference for the synthetic reaction, making it a versatile tool for managing phosphate metabolism in engineered systems.
Figure 1: Basic function of PPK1
Construct features : Promoter: Constitutive promoter for continuous expression. We use tac promoter in our experiment. PPK1 Coding Sequence: Encodes the polyphosphate kinase 1 enzyme. Terminator: Efficient transcription terminator to ensure proper mRNA processing. We use T7Te terminator in our experiment.
Figure 2: Colony PCR indicating plasmid replication in Shewanell
Figure 3: Agarose gel electrophoresis indicating the target gene was successfully introduced into Shewanella
Figure 4: SDS-PAGE results showing that the BBa-B0034 one’s protein expression is the maximum, corresponding to the strength of RBS
Origin (Organism): The PPK1 gene was sourced from Citrobacter freundii.
Experimental Characterization and results: Alteration of protein expression intensity can regulate the metabolic networks, so we focused on RBS with varying translation strengths to facilitate the regulation of PPK1 concentration in Shewanella thus developing the best ability to produce electricity and polymerize phosphorus. Using molybdate assays to determine Pi concentration and half-cell reaction(electrochemistry) to measure the electricity production ability, we found SPK3(with RBS BBa-B0034) has the greatest capacity to polymerize phosphorus but a worst electroproduction capability.
Figure 5: statistical data on electricity production capacity of Shewanella with the introduction of PPK1 with different RBS
Figure 6: statistical data on phosphorus accumulation capacity of Shewanella with the introduction of PPK1 with different RBS
References: 1.Itoh, H., & Shiba, T. (2004). Polyphosphate synthetic activity of polyphosphate:AMP phosphotransferase in Acinetobacter johnsonii 210A. Journal of Bacteriology, 186(15), 5178-5181. Sequence and Features
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