Antisense interaction between r and a

The full length mRNA of scbR (r) binds to the full length mRNA of scbA (a) and form a complex which prevents further translation of both mRNAs.

Chemical equation

$a + r \rightleftharpoons r-a$

Rate equation

Failed to parse (Cannot store math image on filesystem.): r= K_{ar}\cdot [r]\cdot [a]-K_{-ar} \cdot [a-r]

Parameters

The parameters of this reaction is the binding and unbinding rate constant for the interaction of scbR mRNA with scbA mRNA ($K_{ar}$) and ($k^{-}_{ar}$). The parameter values are derived from various RNA/RNA interaction studies in bacteria.

Name	Value	Units	Value in previous GBL models	Remarks-Reference
$K_{ar}$	Failed to parse (Cannot store math image on filesystem.): 0.20-89	$nM$	$0.001 nM^{-1} s^{-1}$ (Bistability range: $6.5 \cdot 10^{-4}-0.16 nM^{-1} s^{-1}$)	In a 1991 review, Y. Eguchi reported association rates for double stranded RNA binding in the range of $1 \cdot 10^{5}-3 \cdot 10^{6} M^{-1} s^{-1}$. A similar range (~$10^{6} M^{-1} s^{-1}$) is published by S. Brantl in a 2007 review on regulatory mechanisms employed by antisense RNAs. Y. Eguchi 1991 S. Brantl 2007 These values are also in agreement with a study by Franch et al. on the effect of a U-turn loop structure in RNA/RNA interactions, who reported binding rate constants $0.15 \cdot 10^{6}-5 \cdot 10^{6} M^{-1} s^{-1}$ and suggested that ~$10^{6} M^{-1} s^{-1}$ is the upper limit for this interaction. Franch et al. 1999 Franch et al. 1999 Finally, Nordgren et al. published a study on the kinetics of antisense RNA interactions by using Surface Plasmon Resonance (in wild-type and mutant RNA pairs), where the values reported for the association rate constants are in the range of $4.5 \cdot 10^{4}-9.2 \cdot 10^{5} M^{-1} s^{-1}$ and the resulting equilibrium dissociation constant are in the range of Failed to parse (Cannot store math image on filesystem.): 8.3 \cdot 10^{-8}-6.9 \cdot 10^{-10} M (Failed to parse (Cannot store math image on filesystem.): 8.3-89 nM ). Nordgren et al. 2001 Assuming that the dissociation rate is in the range of $10^{-3}$, then from the aforementioned association constants, we calculated the equilibrium dissociation constant as per Failed to parse (Cannot store math image on filesystem.): K_D= /frac{k_d}{k_a} . So for the range $0.15 \cdot 10^{6}-5 \cdot 10^{6} M^{-1} s^{-1}$, the $K_D$s are Failed to parse (Cannot store math image on filesystem.): 0.2-6.67 nM .
$k^{-}_{ar}$	Failed to parse (Cannot store math image on filesystem.): 0.006-6	$min^{-1}$	Failed to parse (Cannot store math image on filesystem.): 0.01 nM^{-1} s^{-1} (Bistability range: $0-0.2 s^{-1}$)	In the study by Nordgren et al., dissociation rate constants in the range Failed to parse (Cannot store math image on filesystem.): 4 \cdot 10^{-4}-7.7 \cdot 10^{-3} s^{-1} (0.024-0.0462 min^{-1}) were reported (see figure above). These values are also consistent with the ones published by Lima et al. in a study on antisense oligonucleotide hybridization kinetics, who reported dissociation rate constant values in the range $1 \cdot 10^{-4}-2 \cdot 10^{-2} s^{-1} (0.006-1.2 min^{-1})$ Lima et al. 2001 Although the values retrieved by literature are between $0.006$ and $1.2 min^{-1}$, we wish to explore a wider range of values ($0.006-6 min^{-1}$) in order to take into account the possibility that high GC contents may affect the kinetic rate constants.

Parameters with uncertainty

When deciding how to describe the uncertainty for these parameter we must take into consideration the fact that many of the reported values are derived from in vitro experiments and correspond to mRNA sequences or fragments of different bacteria species. This means that there might be some difference between actual parameter values and the ones reported in literature. These facts influence the quantification of the parameter uncertainty and therefore the shape of the corresponding distribution.

With regards to the $K_{ar}$ the values that are mostly encountered in different publications are in the range $1-10 nM$, therefore we put the weight of the distribution in this range and we consider as least likely the larger values. Therefore, the mode of the log-normal distribution is set to $5 nM$ and the confidence interval factor Failed to parse (Cannot store math image on filesystem.): 1.5 . This means that the mode of the PDF is 0.1 and the range where 95% of the values are found is between 0.067 and 0.15.

Similarly, the most plausible parameter value for the Failed to parse (Cannot store math image on filesystem.): K_{-ar} is decided to be Failed to parse (Cannot store math image on filesystem.): 0.6 and the confidence interval Failed to parse (Cannot store math image on filesystem.): 0.1 . This means that the mode of the PDF is 0.6 and the range where 95% of the values are found is between 0.06 and 6.

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

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The location and scale parameters of the distribution are:

Parameter	μ	σ
$K_{ar}$	Failed to parse (Cannot store math image on filesystem.): -2.2618	Failed to parse (Cannot store math image on filesystem.): 0.2020
Failed to parse (Cannot store math image on filesystem.): K_{-ar}	$0.3043$	$0.9028$