Structural Basis for the Inhibition of Helicobacter pylori α-Carbonic Anhydrase by Sulfonamides
Fig 5
Structural comparison between the MZA and AAZ complexes of HpαCA.
The MZA molecule is shown in all-atom representation with carbon atoms coloured in orange. The (mFo-DFc) sigmaA-weighted electron density for MZA is shown in green. The map was calculated at 2.2-Å resolution and contoured at 3.0-σ level. The AAZ molecule is shown in cyan. Protein surface is shown and coloured according to the electrostatic potential. The subtle rotation and shift of MZA with respect to AAZ does not break the hydrogen bond between the O3 atom of the carbonamide moiety and the side chain of Asn108. The weaker binding of MZA in comparison to AAZ is likely due to energetically unfavourable interaction between the additional aliphatic methyl group of MZA and partially negatively charged carbonyl oxygens of the main-chain peptides of Ala192 (C-O distance 4.3 Å) and Pro193 (C-O distance 3.5 Å).