Measurement

Part:BBa_K1682013

Designed by: iGEM15_HKUST-Rice   Group: iGEM15_HKUST-Rice   (2015-09-02)
Revision as of 16:14, 15 September 2015 by Lytangaa (Talk | contribs) (Biology of PphoA)

PphoA -I13504- phosphate responsive promoter with GFP generator

Biology of PphoA

Fig.1 Phosphate sensing mechanism of PphoA.

Escherichia coli (E. coli) detects inorganic phosphate (P(i)) from the environment by the PhoR/PhoB two-component system (Hsieh & Wanner, 2010). As illustrated in Figure 1, PphoA is cross-regulated by PhoB and PhoR. The sensory histidine kinase PhoR behaves either as an activator or inactivator for PhoB depending on different states (inhibition state, activation state, deactivation state). When phosphate is limited, PhoR acts as a phospho-donor for the autophosphorylation of PhoB. The phosphorylated PhoB will directly activate PphoA. In contrast, when there is phosphate, PhoR interferes with phosphorylation of PhoB which in turn inactivates PphoA.

Constructs for characterization

Fig.2 Phosphate sensing construct with reporter.

With the phosphate (pho) regulon from E. coli, it can be utilized for detecting phosphate level. To make a phospahte-sensing device, we obtained the promoter, PphoA, and combined it with a GFP reporter, BBa_E0240, in BioBrick RFC10 standard so that the promoter activity in different potassium level can be detected and characterized.

RFU measurement

Fig.3 Activity of PphoA in E. coli DH10B in different phosphate concentrations

As shown in Figure 3, PphoA is induced under phosphate limitation and repressed under high phosphate concentration. The fluorescence intensity dropped by 2.99 folds between 0 to 200μM concentration of phosphate. Furthermore, a plateau is observed starting from the 200 μM phosphate concentration point, suggesting that the dynamic range of PphoA is from 0-200 μM of phosphate.

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
    INCOMPATIBLE WITH RFC[1000]
    Illegal BsaI.rc site found at 755


[edit]
Categories
//chassis/prokaryote/ecoli
//classic/measurement/uncategorized
//function/sensor
Parameters
None