Part:BBa_K5034212

PolyP + AMP --> ADP

This basic part encodes the PAP gene which is initially from Acinetobacter johnsonii and we performed codon optimization on, is expressed in the PYYDT plasmid. This basic part is designed to facilitate the reversible conversion of inorganic polyphosphate (PolyP) and adenosine monophosphate (AMP) to adenosine diphosphate (ADP). The PAP enzyme plays a crucial role in phosphate and energy metabolism. PAP and PPK2 have strong poly(P) utilization activity, and the activity of PAP is 20-fold higher than that in PPK1, even though the Km values for utilization of all three enzymes are almost the same. This implies that PAP and PPK2 work mainly for poly(P) utilization in the cell. However, PAP has the same level of poly(P) synthetic activity (Km and Vmax) as PPK1, and this suggests that PAP also works for poly(P) synthesis at a significant level.

Figure 1: Basic function of PAP

Sequence and Features

Assembly Compatibility:

10
COMPATIBLE WITH RFC[10]
12
COMPATIBLE WITH RFC[12]
21
COMPATIBLE WITH RFC[21]
23
COMPATIBLE WITH RFC[23]
25
COMPATIBLE WITH RFC[25]
1000
COMPATIBLE WITH RFC[1000]

Construct features

Promoter: Constitutive promoter for continuous expression. We use tac promoter in our experiment.
RBS: BBa_B0034
PAP Coding Sequence: Encodes the polyphosphate:AMP phosphotransferase enzyme.
Terminator: Efficient transcription terminator to ensure proper mRNA processing. We use T7Te terminator in our experiment.

Figure 3: PCR of target genes PCR before plasmids construction (The extra small fragment in the picture is primer dimer)

The length of the PAP gene is about 1428 base pairs, which is consistent with the results on the DNA electropherogram, proving that we have obtained the PAP gene.

Origin (Organism)

The PAP gene was sourced from Acinetobacter johnsonii.

Experimental Characterization and results

In our team’s previous research we found that the behavior of the modified S. oneidensis 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 S. oneidensis. Electricity production: Using half-cell reaction(electrochemistry) to measure the electricity production ability. Capacity to polymerize phosphorus: Conducting molybdate assays to determine Pi concentration. Conducting molybdate assays to determine Pi concentration and found that PAP do not have a good capacity to polymerize phosphorus (but better than PPN1 and PPX). Details of all experiments can be found at the Experiments section on the Wiki.

Figure 3: Statistical data on electricity production capacity of S. oneidensis with the introduction of different hydrolases

Figure 4: Statistical data on the phosphorus accumulation capacity of S. oneidensis with PAP

Figure 5: ATP level in S. oneidensis with the introduction of different hydrolases

Chassis and genetic

Chassis：Shewanella oneidensis MR-1.

The gene can be expressed and function properly in S. oneidensis.

Potential applications

PAP, as an enzyme class for the synthesis of ADP, plays an important role in the synthesis of intracellular high-energy phosphate compounds and is a key enzyme in the regulation of the intensity of intracellular metabolism

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.