Figure 1.

Three-dimensional structure of TxGH116 β-glucosidase. (A) Three views of the three-dimensional structure of TxGH116. The N-terminal domain consists of β-sheets (sheets 1–3) surrounded by α-helices (H1–H4). The C-terminal (α/α)₆ solenoid domain contains the active site and consists of 12 α-helices (H5–H16) in six outer helix plus inner helix pairs, with H5 situated between the two domains. A long loop with a two-strand β-sheet (sheet 5) lies between helices H7 and H8, near the active site (E441 and D593). α-Helices are shown in blue and β-strands in yellow. (B) Active site residues of the native structure of TxGH116, showing the distance between the catalytic nucleophile (E441) and acid/base (D593) carbons (red labels). (C) Active site of the TxGH116 covalent intermediate complex with 2-deoxy-2-fluoroglucose, showing the distance between the catalytic residues is decreased in this intermediate. Distances between the geometric means of the carboxyl groups are slightly shorter and are given in the text. Distances are in Å.