Difference between revisions of "Part:BBa K2739000"

Revision as of 11:37, 11 October 2018

ProR-PhaR (The phasin autoregulation system with native promoter)

This is a composite part designed to investigate the role of the phaR autoregulation system on cell growth and PHA production. PhaR is the core member of the phasin autoregulation system, which contribute to the PHA operon and PHA production. It is known to repress the expression of the phasin through binding to the phasin promoter and auto-regulate its own expression. Otherwise, phaR can also bind to the PHB granules. This part verify the novel function of phaR in PHA production when the recombinant E.coli is coexpressed with PHA operon.

coupled with 

with and without Phasin or Phasin-HlyA. 

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.

Through the coexpression of the PHA operon, the influence of phaR autoregulation system on PHB production and cell growth rate would be investigated.

coupled with phasin

recombinant E.coli harbouring phaCAB operon + phaR autoregulation system + phasin was constructed to investigated the

Usage and Biology

According to previous research (Pötter et al, 2002), 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 σ70 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). Based on the binding behaviours and following influence, it was confirmed that phaR regulated not only phaP but also itself precisely (Pötter et al, 2002).

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 phasin 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 phasin as well as curtailing excessive expression of the PHA biosynthetic pathway, decreasing the metabolic burden imposed on cells.

Sequence and Features