TY - JOUR
T1 - Robustness and the cycle of phosphorylation and dephosphorylation in a two-component regulatory system
AU - Batchelor, Eric
AU - Goulian, Mark
PY - 2003/1/21
Y1 - 2003/1/21
N2 - The EnvZ/OmpR system in Escherichia coli, which regulates the expression of the porins OmpF and OmpC, is one of the simplest and best-characterized examples of two-component signaling. Like many other histidine kinases, EnvZ is bifunctional; it phosphorylates and dephosphorylates the response regulator OmpR. We have analyzed a mathematical model of the EnvZ-mediated cycle of OmpR phosphorylation and dephosphorylation. The model predicts that when EnvZ is much less abundant than OmpR, as is the case in E. coli, the steady-state level of phosphorylated OmpR (OmpR-P) is insensitive to variations in the concentration of EnvZ. The model also predicts that the level of OmpR-P is insensitive to variations in the concentration of OmpR when the OmpR concentration is sufficiently high. To test these predictions, we have perturbed the porin regulatory circuit in E. coli by varying the expression levels of EnvZ and OmpR. We have constructed two-color fluorescent reporter strains in which ompF and ompC transcription can be easily measured in the same culture. Using these strains we have shown that, consistent with the predictions of our model, the transcription of ompC and ompF is indeed robust or insensitive to a wide range of expression levels of both EnvZ and OmpR.
AB - The EnvZ/OmpR system in Escherichia coli, which regulates the expression of the porins OmpF and OmpC, is one of the simplest and best-characterized examples of two-component signaling. Like many other histidine kinases, EnvZ is bifunctional; it phosphorylates and dephosphorylates the response regulator OmpR. We have analyzed a mathematical model of the EnvZ-mediated cycle of OmpR phosphorylation and dephosphorylation. The model predicts that when EnvZ is much less abundant than OmpR, as is the case in E. coli, the steady-state level of phosphorylated OmpR (OmpR-P) is insensitive to variations in the concentration of EnvZ. The model also predicts that the level of OmpR-P is insensitive to variations in the concentration of OmpR when the OmpR concentration is sufficiently high. To test these predictions, we have perturbed the porin regulatory circuit in E. coli by varying the expression levels of EnvZ and OmpR. We have constructed two-color fluorescent reporter strains in which ompF and ompC transcription can be easily measured in the same culture. Using these strains we have shown that, consistent with the predictions of our model, the transcription of ompC and ompF is indeed robust or insensitive to a wide range of expression levels of both EnvZ and OmpR.
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U2 - 10.1073/pnas.0234782100
DO - 10.1073/pnas.0234782100
M3 - Article
C2 - 12522261
AN - SCOPUS:0037457896
SN - 0027-8424
VL - 100
SP - 691
EP - 696
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 2
ER -