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Figure 1.
Figure 1. Schematic diagram of the CysB-binding sites (CBS)
at the cysJIH, cysK cysP and cysB promoters. The boxes represent
19 base pair sequences believed to represent half-sites to which
a single subunit binds [3]. At activation sites (purple),
N-acetylserine stimulates CysB binding and activates
transcription. N-acetylserine also stimulates binding to the
accessory sites (white). N-acetylserine inhibits binding to
CBS-B (red) partially relieving repression at the cysB promoter.
The cofactor also diminishes binding to the accessory site
CBS-K2 (green). Finally, N-acetylserine can also influence the
extent of bending induced by binding at the cysK and cysP
promoters. Bending at points indicated by arrows is induced by
binding to both the activation site and to either half-site K2c
or P3b (orange). N-acetylserine prevents binding at the latter
and simultaneously stimulates binding at the activation sites.
(The figure is adapted from Colyer and Kredich [27].)
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