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Team:UC Davis/PhoR ChvI1
From 2009.igem.org
PhoR-->ChvI
It
has been hypothesized
that due to the amino acid similarity of ChvI to PhoB, ChvI is able to
act as a
phosphate regulator in E.coli as a PhoB substitute (3).
Since
ChvI showed no abnormal activity
inside Agrobacterium tumefaciens under phosphate
limitation, it
cannot serve as the primary phosphate regulator in A. tumefaciens
(3).
Note: ChvI was not required for phosphate regulation
in A. tumefaciens (3), but it might be involved in phosphate
regulation in A. tumefaciens in some way (3). Therefore, the
possibility of crosstalk still exists
Due to the structural similarity
of
ChvI and PhoB, the possibility of crosstalk exists (3).
Note: Since
we are going to use E. coli as our model chassis for this
project; we
had to make sure that our proteins will keep their characteristics of
our
interest after being placed inside the E. coli.
For example, VirG gene (promoter 1) after being introduced
into E. coli cells, started to behave as if it were a member of
phosphate
regulon (note: PhoB function was necessary for virG induction by
phosphate
starvation)(6). Studies have suggested that the reason for this
behavior
was due to the fact that virG promoter 1 has two hexamer blocks which
have the
same positions as the pho genes (6).
Studies have shown that ChvI probably activated Alkaline
Phosphatase (AP)
activity by activating transcription of PhoA (PhoA also gets activated
by PhoB)
(3). It was not proven that ChvI activates other PhoB-dependent
promoters or
recognizes the same DNA sequence as PhoB (3). However, there has been
speculation
that since PhoR mediates PhoB phosphorylation and dephosphorylation, it
may do
the same to ChvI(3).
Therefore, the best option would be to find a promoter
from A. tumefaciens that gets activated by ChvG/ChvI, a
two-component
regulatory system only; and does not interact with any E. coli
system.
