Change in conc. of membrane phoQ In order to capture the effects of varying the rate of diffusion of Mg2+ on the system output, the simulation was ran with increasing Mg2+ diffusion rates (with means of 100ms, 1ms and 10ms). The results have been reported for two key system resources, the proteins phoQ, which is the sensory protein responsible for binding to Mg2+, and the phoP protein, which controls the dynamics of gene expression. The figure shows how the rate of decrease in the concentration of inactive phoQ (phoQ molecule bound to a Mg2+) is damped with increasing delay in the diffusion of Mg2+ out of the membrane. Also, captured in this graph is the effect of resource starvation on the biological system. As the Mg2+ ion initiated signal activates the PhoPQ pathway, the sensory phoQ proteins are consumed by the system, thereby shutting down the pathway when all phoQ molecules available to the system have been used.
Ghosh et al. BMC Genomics 2010 11(Suppl 3):S3 doi:10.1186/1471-2164-11-S3-S3