Response to localized production of X. This figure shows how the steady state spatial distribution of the complexes in response to varying rates of production of nondiffusible X. A and B are produced at a uniform rate across the domain, while X is produced in a localized region. a) shows the spatial distribution of BX as production of X changes, where both A and AX are diffusible. This allows BX to spread over the whole cell, even though it is not diffusible. The distribution of BX is almost uniform for low levels of production of X. b) shows the spatial distribution of BX as production of X changes, where A is the only diffusible component. Here a pronounced localization is observed. In both cases the AX profile is spatially uniform (not shown).