Binding of R2 to OA operator

The ScbR homo-dimer (R₂) binds to the ScbA gene promoter (O_A) and represses its mRNA transcription.

Chemical equation

$O_{A} + 2R_{2} \rightleftharpoons O_{A}-R_{2}$

Rate equation

$r= \frac{k^{-}_{2}}{K_{d2}}\cdot [O_{A}]\cdot [R_{2}]^{2} - k^{-}_{2}\cdot [O_{A}-R_{2}]$

Parameters

The parameters of this reaction are the dissociation constant for binding of ScbR to O_A ($K_{d2}$) and the dissociation rate for binding of ScbR to O_A ($k^{-}_{2}$).

Parameter	Value	Origin	Remarks
$K_{d2}$	$0.1 - 5.6 nM$	TetR-tetO interaction and TetR-like Rv3066 from M. tuberculosis	Repressor protein TetR binds to the operator tetO, repressing its own expression and that of the efflux determinant tetA. Similar structure and activity as ScbR binding to OA
$k^{-}_{2}$	$0.6-1.2 min^{-1}$	SPR of a TetR-like protein (RolR) on a Gram and GC content ~ 50-60% from Corynebacterium glutamicum

Parameters with uncertainty

The most plausible parameter values and the confidence interval were decided to be:

$K_{d2} = 5 \pm 0.6 nM$

$k^{-}_{2}= 0.9 \pm 0.3 min^{-1}$

The probability distributions, adjusted accordingly in order to reflect the above values, are the following: