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. Author manuscript; available in PMC: 2012 Oct 2.
Published in final edited form as: Nat Struct Mol Biol. 2012 Jul 15;19(8):767–772. doi: 10.1038/nsmb.2340

Figure 4.

Figure 4

Proposed mechanism for macrocyclization. (a) Model of the acyl-enzyme intermediate with AYDG remaining bound at the active site. (b) The acyl-enzyme intermediate is in equilibrium with the substrate. In PatGmac the N terminus of the substrate enters the active site, displacing AYDG and leading to macrocyclization. Mutations that disrupt binding of AYDG lead to linear product, as the substrate is hydrolyzed by water. The role of the histidine in deprotonating the incoming N terminus is speculative.