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Figure 5.
Figure 5. A Conserved Cluster of Phenylalanines Protects the
Peptidyl-Imidate Intermediate from Hydrolysis and Base Exchange
with Nicotinamide
(A) Cluster of phenylalanine side chains
(red), Phe33, Phe48, and Phe162, that shield the S-alkylamidate
intermediate from solvent. (B) Orientation of Phe33 side chain
in the Michaelis complex (blue) and in the structure containing
the S-alkylamidate intermediate (grey). (C) Conformation of Phe
33 in the Sir2Tm-S-alkylamidate intermediate (pink) as compared
with its position in the structure of Sir2Tm bound to the
deacetylation reaction product, nicotinamid (green; PDB ID code
2H4J).
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