Proposed model for the function of the Rsb regulatory system in <i>Chlamydia</i>.

<p>Under steady-state conditions, the expression levels and activies of RsbU_Ct (purple), RsbV1 (black), and RsbW_Ct (red) provide an equilibrium in which σ⁶⁶ availability is ample for normal growth and development (A). Upon an accumulation of active (<i>i</i>.<i>e</i>. non phosphorylated) RsbV1 via increased expression or increased activity/expression of RsbU_Ct, the equilibrium of RsbW_Ct function shifts away from the anti-sigma factor role, allowing increased transcription of σ⁶⁶-promoted genes (B). Upon the decreased availability of active RsbV1 (either through reduced expression or reduced RsbU_Ct expression/activity), the equilibrium of RsbW_Ct function is driven towards the anti-sigma factor function, limiting the amount of σ⁶⁶ that is available for association with the core RNAP complex (C).