Stereoviews of the AMP complex of the Q32R hmFru-1,6-Pase.

<p>The metal ions and water molecules are represented by magenta and green spheres, respectively in hmFru-1,6-Pase. The carbon atoms for the hmFru-1,6-Pase and AMP are in yellow and white, respectively. A. The presence of a metaphosphate (PO₃) and metal ions (labeled M1, M1′, M2 and M3) in the active site. The Fourier difference maps with the above atoms omitted for calculation cover the metaphosphate molecule and metal ions at a contour level of 6σ. B. Interactions between AMP and the binding pocket. The Fourier difference map for AMP contoured at 2.5σ is shown as a green mesh. Direct and water-mediated H-bonds are depicted by black dash lines. The water molecules contributing to AMP binding are labeled: the water W40 connecting the phosphate moiety and the adenine moiety is commonly observed in hmFru-1,6-Pase and other Fru-1,6-Pases, whereas W115 and W183 are unique to hmFru-1,6-Pase. C. Superposition of the AMP binding pocket of hmFru-1,6-Pase (residues labeled in black), and human liver Fru-1,6-Pase (PDB 1FTA)(residues labeled in red). The carbon atoms for the human liver Fru-1,6-Pase are colored salmon, and the two water molecules (O367 and O381) bound in the pocket (albeit too far to form H-bonds to AMP) are represented by red spheres and their interactions with human liver Fru-1,6-Pase are shown as magenta dashed lines. The flip of the peptidyl bond connecting residues 177 and 178 resulting from sequence variation between hmFru-1,6-Pase and human liver Fru-1,6-Pase in this region is indicated by the black asterix.