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Figure 3.
Figure 3. CTD Dephosphorylation and Close-Up Views of the
Fcp1 Active Site
(A) Two-step Fcp1 reaction pathway. Step 1
is the attack of the active-site aspartate on the phosphorus of
phospho-CTD to form an acylphosphate intermediate. Step 2
entails a nucleophilic attack by water on the acylphosphate,
resulting in formation of the inorganic phosphate product.
(B) Stereo view of the active site of Fcp1-Mg-BeF[3] complex
that mimics the acylphosphate intermediate.
(C) Stereo view
of the Fcp1-Mg-AlF[4]^− complex that mimics the step 2
transition state. Side chains are depicted in stick
representation; Mg and water are denoted by blue and red
spheres, respectively. The proposed nucleophilic water is
labeled Wat^*. Atomic contacts are indicated by dashed lines.
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