A Model for Sigma Factor Competition in Bacterial Cells
Figure 6
(A) During the stringent response RNA polymerases involved in rRNA transcription are quickly released to increase the pool of free cores. (B) Number of holoenzymes and
as a function of the copy number of core RNAPs. The black dashed lines show the number of available RNAPs during the exponential growth state (
) and during the stringent response state. The gray region shows the range of core RNAP for which there is sigma factor competition. (C) Response factor
of the alternative sigma factor-dependent gene transcription (with
M) to an increase of concentration of RNAPs. The blue dashed line shows the maximal sensitivity, that for strong core-sigma binding, is found for
and lies in the competition region. (D) Number of alternative holoenzymes and (E) response factor
related to the σAlt-dependent gene transcription as a function of the number of core RNAPs and alternative sigma factors (with
M). The white line encloses the region of sigma factor competition. The points show possible values of cores and alternative sigma factors for a cell in the exponential growth state and in the stringent state.