Architecture and Trade-offs in the Heat Shock Response System

Abstract

Biological control systems often contain a wide variety of feedforward and feedback mechanisms that regulate a given process. While it is generally assumed that this apparent redundancy has evolved for a reason, it is often unclear how exactly the cell benefits from more complex circuit architectures. Here we study this problem in the context of a minimal model of the Heat Shock Response system in E. coli and show, through a combination of theory and simulation, that the complexity of the natural system outperforms hypothetical simpler architectures in a variety of robustness and efficiency tradeoffs. We have developed a significantly simplified model of the system that faithfully captures these rich issues. Because a great deal of biological detail is known about this particular system, we are able to compare simple models with more complete ones and obtain a level of theoretical and quantitative insight not generally feasible in the study of biological circuits. We primarily hope this will inform future analysis of both heat shock and newly studied biological complexity.