An Inserted α/β Subdomain Shapes the Catalytic Pocket of Lactobacillus johnsonii Cinnamoyl Esterase
Figure 3
Schematic diagram of LJ0536-substrate interactions.
The substrate and products are highlighted in bold. Dotted line represents hydrogen bonds. Curved line represents the hydrophobic cavity created by Phe34, Phe160, and Leu165. The 3-methoxy group of the ferulic ring is oriented towards the hydrophobic cavity. Asp138 is hydrogen bonded to the 4-hydroxyl group on the ring of ferulic and caffeic acid. Tyr169 is hydrogen bonded to the 3-hydroxyl group of caffeic acid ring. The oxyanion hole is formed by the backbone nitrogen atoms of Phe34 and Gln107. (A) Ethyl ferulate bound. The distance between the catalytic serine hydroxyl group and the ester carbon is 2.1 Å and 2.3 Å in chain A and chain B, respectively. (B) Ferulic acid bound. The distance between the catalytic serine hydroxyl group and the ester carbon is 2.0 Å. (C) Caffeic acid bound. The distance between the catalytic serine hydroxyl group and the ester carbon is 2.2 Å and 2.0 Å in chain A and chain B, respectively. Note that distances between the catalytic serine hydroxyl group and ester carbons are based on modeling the serine rotamer seen in the WT structure (t rotamer, chi angle = −178) onto the structures of the S106A mutant-substrate complexes.