Module-based analysis of robustness tradeoffs in the heat shock response system.
Biological systems have evolved complex regulatory mechanisms, even in situations where much simpler designs seem to be sufficient for generating nominal functionality. Using module-based analysis coupled with rigorous mathematical comparisons, we propose that in analogy to control engineering architectures, the complexity of cellular systems and the presence of hierarchical modular structures can be attributed to the necessity of achieving robustness. We employ the Escherichia coli heat shock response system, a strongly conserved cellular mechanism, as an example to explore the design principles of such modular architectures. In the heat shock response system, the sigma-factor sigma32 is a central regulator that integrates multiple feedforward and feedback modules. Each of these modules provides a different type of robustness with its inherent tradeoffs in terms of transient response and efficiency. We demonstrate how the overall architecture of the system balances such tradeoffs. An extensive mathematical exploration nevertheless points to the existence of an array of alternative strategies for the existing heat shock response that could exhibit similar behavior. We therefore deduce that the evolutionary constraints facing the system might have steered its architecture toward one of many robustly functional solutions.
Kurata
Hiroyuki
H
Department of Bioscience and Bioinformatics, Kyushu Institute of Technology, Iizuka, Fukuoka, Japan. kurata@bio.kyutech.ac.jp
El-Samad
Hana
H
Iwasaki
Rei
R
Ohtake
Hisao
H
Doyle
John C
JC
Grigorova
Irina
I
Gross
Carol A
CA
Khammash
Mustafa
M
D003198:Computer Simulation; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D005246:Feedback / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D018869:Heat-Shock Response / Q000502:physiology*; D008954:Models, Biological; D018384:Oxidative Stress / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D049490:Systems Biology / Q000379:methods
D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins