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![[Figure 10]](ba5257fig10mag.jpg)
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Figure 10
Conformational validation. (a) Chemical errors in the key TM9 sugar, deposited as an N-acetyl α-L-mannosamine derivative (left, PDB entry 4k3t, now superseded by PDB entry 5awv), and their impact on the published structure (right). (b) Correct stereochemistry (left) and re-refined structure after correcting the errors (right). Re-refining the structure with the correct stereochemistry (N-acetyl β-D-glucosamine derivative) causes the sugars to end up in the minimal energy chair conformation. For the stereochemically correct ligand, OMIT density maps (mFo − DFc coefficients, contoured at 2σ) show plausible density for the putative diol intermediate at least in chains M and N. While the maps selected by the original authors may not be too different from those obtained through refinement of the correct chemical species at the C6 diol, publishing a distorted sugar with the wrong stereochemistry at almost every position casts legitimate doubt on their glyco-chemical conclusions. This figure was generated with CCP4mg (McNicholas et al., 2011  ). |
![[Figure 10]](ba5257fig10.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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