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. Author manuscript; available in PMC: 2013 Oct 26.
Published in final edited form as: Mol Cell. 2012 Sep 13;48(2):231–241. doi: 10.1016/j.molcel.2012.08.009

Figure 3. pppGpp Mediates Feedback Control of GTP Levels.

Figure 3

(A) pppGpp levels increase concomitantly with increased GTP levels in WT cells following guanosine treatment (Guo). 32P-labeled WT cells were treated with 1 mM Guo. At the indicated times after treatment, nucleotides were extracted, measured by TLC, and normalized to T=0.

(B) Schematic of a negative feedback loop of GTP synthesis with pppGpp.

(C) Two-dimensional TLC of 32P-labeled nucleotides with ATP and GTP indicated. WT (left panels) and (p)ppGpp0 (right panels) cells before (upper panels) and 20 minutes after addition of 1 mM Guo (lower panels) are shown.

(D–E) Quantification of GTP (D) and ATP (E) levels by LC-MS/MS of WT (red) and (p)ppGpp0 (blue) cells in a time course after treatment with 1 mM Guo, normalized to T=0.