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. Author manuscript; available in PMC: 2014 Jan 1.
Published in final edited form as: Biochim Biophys Acta. 2012 Sep 6;1829(1):20–28. doi: 10.1016/j.bbagrm.2012.08.009

Figure 4. Two-metal catalysis of NTP condensation by yeast RNA polymerase II.

Figure 4

Figure 4

Figure 4

A. RNA 3′ OH is deprotonated by the OH− from the bulk solvent as substrate’s Oβ is protonated by His1085. B. Nucleophilic attack by RNA 3′ O− on substrate’s Pα. C. Substrate in a form of NMP added to the 3′ end of RNA, pyrophosphate in a form of protonated (Mg-PPi)− leaves active site. This figure was adapted from Carvalho et al97, and shows reaction mechanism as a sequence of distinct steps, for clarity and ease of analysis. Proton-inventory experiments reported by Castro et al. indicated that these reaction can take place within the same associative-like transition state82.