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. Author manuscript; available in PMC: 2022 Jul 20.
Published in final edited form as: Nat Chem. 2020 Aug 10;12(10):968–972. doi: 10.1038/s41557-020-0515-3

Extended Data Fig. 4. A proton relay conveys protonation of GG-DHB.

Extended Data Fig. 4

(A) The structure of MstE:FS-DHB superpositioned with MstE_D109N:GG-DHB (RMSD-Cα: 0.12 Å) reveals that Asp109 adopts anti-position for protonation of the terminal C=C in GG-DHB. Two water molecules align between Tyr216 and Asp109 to activate the Brønsted acid and replace the proton after reaction. Oxygen atoms are highlighted in red; the protons (light blue) were added with PyMol (37) and oriented according to potential interactions represented as dashed lines (distance given in Å). (B) The primary amine of Asn109 in MstE_D109N:GG-DHB displaces one of the water molecules by 0.6 Å, flipping the orientation of all protons in the cluster.