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Figure 2
WT and E82I PaDsbA1 have a high degree of global structural equivalence with localized conformational differences. (a) Structural superposition of E82I PaDsbA1 (global superposition over all equivalent Cα atoms) on WT PaDsbA1 (PDB entry 3h93 ) shows a high similarity (r.m.s.d. of 0.94 Å between 180 equivalent Cα atoms). WT and E82I PaDsbA1 are coloured blue and orange, respectively, throughout. The connecting α-helix H6 in both WT and E82I PaDsbA1 overlaps precisely, and the thioredoxin domain also superimposes well. The main differences between the two structures localize primarily in the H2–H3 turn and N-terminal region of H3. The catalytic surface loops (CHPC active site, L1, cis-Pro L2 and L3) are highlighted (blue and orange for WT and E82I PaDsbA1, respectively). The side chain of active-site His39 that undergoes rotation in crystals 2 and 3 relative to crystal 1 and WT PaDsbA1 is shown in stick representation. (b, c) Close-up view of the H2–H3 turn and N-terminal region of H3. The view in (c) is rotated 180° around the y axis relative to (a) and that in (b) is rotated 45° around the x axis relative to (c). The E82I substitution disrupts the hydrogen-bonding pattern in this region, which introduces a kink and a partial helical turn to the N-terminal part of H3 in the E82I structure relative to the wild type. (d) Hydrogen-bonding pattern in the H2–H3 region of PaDsbA1. The side chain of His91 is hydrogen-bonded to the side chains of Glu82 and Tyr35. (e) Hydrogen-bonding pattern in the H2–H3 region of E82I PaDsbA1. Mutation of Glu82 to Ile results in the reorientation of His91, Glu87 and Glu44. In the E82I variant protein the side chain of His91 is connected by hydrogen bonds to the side chains of Glu87 and Glu44. (d) and (e) are orientated as in (c).

Journal logoBIOLOGICAL
ISSN: 1399-0047
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