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Figure 3.
Figure 3. Tgt and ppGpp bind to overlapping sites on RNAP.
(a) Superposition of the ttRNAP-Tgt and ttRNAP-ppGpp complexes.
The color scheme is the same as in Figures 1a and 2a. (b,c)
Structural determinants probably crucial for Tgt and ppGpp
binding. The RNAP-Tgt (b) and RNAP-ppGpp (c) complexes are shown
in the same orientation for better comparison. Residues that are
not identical between E. coli and T. thermophilus are marked by
their numbers only. RNAP residues (balls and sticks) that
interact with both Tgt and ppGpp are shown in green, whereas
those specific for Tgt and ppGpp are shown in light cyan and
light pink, respectively. (d) ppGpp and DksA compete with Tgt
for the inhibition of abortive transcription by the wild-type
ecRNAP from the T7A1 promoter. The assay was conducted as in
Figure 2d. ppGpp was added to 0.5 mM, DksA to 500 nM.
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