Part:BBa_K2739002

Codon optimizated PhaR (The Phasin autoregulation system)

PhaR is the core member of the phasin autoregulation system, which contribute to the PHA operon and PHA production. This sequence is codon optimizated for e coli. Phasin is a low-molecular weight protein that plays a role in PHA granule formation by physically binding to the PHA granule surface and promote the PHA production. The expression of phasin is repressed by an autoregulator phaR, which is able to bind to the region of phasin promoter and its own promoter to regulate the expression of phasin and itself. Otherwise, phaR can also bind to the PHB granules. It is potential to help cells saving energy by curtailing excessive expression of PHA biosynthesis pathways.

This part is not submitted but the sequence is used to develop the construct BBa K2739000 (proR-PhaR), BBa_K2739005 (proR-PhaR-Pha promoter-PhaP) and BBa K27390006 (proR-PhaR-proP-PhaP-HlyA), which allow the further investigation of phaR's function.

Usage and Biology

PhaR binds at two sites upstream of phaP. One site is the transcriptional initiation site plus the -10 region. The other site is a region just upstream of the -35 region of the σ 70 promoter of phaP. Gene of phaR was also recognised to bind to 86 bp upstream of the start codon in the open reading frame (ORF) of phaR. In addition, PhaR was detected binding on the surface of PHA granules (Pötter et al, 2002; Yamada et al, 2013). Before the biosynthesis of PHA or under the condition less favourable for biosynthesis, the phaR repressor binds to the phaP promoter and repress the transcription of phaP. After the onset of PHA biosynthesis, when the nascent PHB granules gradually form, PhaR leaves phaP promoter and binds to PHA granules so that phaP is transcribed and translated (Yamada et al, 2013).During the later stages of PHA accumulation, PhaR leaves the PHA granules as the surface of PHA granules is mostly covered with phasin. The replaced PhaR returns to bind to the phaP promoter and represses transcription of phaP again. PhaR has been reported to autoregulate the expression of itself by binding on its promoter (Yamada et al, 2013). This autoregulation system guarantees the efficient expression of PhaP as well as curtailing excessive expression of the PHA biosynthetic pathway, decreasing the metabolic burden imposed on cells.

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 SapI.rc site found at 147