2018
DOI: 10.1107/s2059798318002541
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Validation of ligands in macromolecular structures determined by X-ray crystallography

Abstract: Better metrics are required to be able to assess small-molecule ligands in macromolecular structures in Worldwide Protein Data Bank validation reports. The local ligand density fit (LLDF) score currently used to assess ligand electron-density fit outliers produces a substantial number of false positives and false negatives.

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Cited by 61 publications
(45 citation statements)
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“…Compared to the VIM‐1:ML302F complex, binding of hydrolysed meropenem to VIM‐2 is less well defined – in addition to the lower resolution, elevated B‐factors were observed for the hydrolysed meropenem ligand (overall B‐factor of 39.13 Å 2 compared to 16.99 Å 2 for the protein main chain). Nevertheless, refining the ligand at full occupancy yielded a real‐space correlation coefficient of 0.85 and real‐space R‐value of 0.25; parameters that indicate acceptable agreement of observed and calculated electron densities for bound ligand . This is confirmed by visual inspection; omit (| F o | − | F c | Φ calc ; Fig.…”
Section: Resultssupporting
confidence: 55%
See 1 more Smart Citation
“…Compared to the VIM‐1:ML302F complex, binding of hydrolysed meropenem to VIM‐2 is less well defined – in addition to the lower resolution, elevated B‐factors were observed for the hydrolysed meropenem ligand (overall B‐factor of 39.13 Å 2 compared to 16.99 Å 2 for the protein main chain). Nevertheless, refining the ligand at full occupancy yielded a real‐space correlation coefficient of 0.85 and real‐space R‐value of 0.25; parameters that indicate acceptable agreement of observed and calculated electron densities for bound ligand . This is confirmed by visual inspection; omit (| F o | − | F c | Φ calc ; Fig.…”
Section: Resultssupporting
confidence: 55%
“…13 A 2 compared to 16.99 A 2 for the protein main chain). Nevertheless, refining the ligand at full occupancy yielded a real-space correlation coefficient of 0.85 and real-space R-value of 0.25; parameters that indicate acceptable agreement of observed and calculated electron densities for bound ligand [37]. This is confirmed by visual inspection; omit (|F o | À |F c | Φ calc ; Fig.…”
Section: Interactions Of Vim-1 With Hydrolysed Meropenemsupporting
confidence: 58%
“…Quite common are issues with small-molecule ligands where mistakes may happen in determining their identity, placement, orientation and conformation. Since ligands by their nature are infinitely more varied than the standard amino acids and nucleotides, they are more difficult to build, refine and validate [37] [38] [39] [40] [41]. …”
Section: Validation Of Structural Data and Models Is (Still) Necessarymentioning
confidence: 99%
“…In an accompanying publication (Smart et al, 2018) we specifically examine ligand validation and the relevant metrics, showing that further work is required to make the latter more reliable.…”
Section: Using Validation Informationmentioning
confidence: 99%
“…residues that show a poorer than expected fit to the electron density. This is followed by a table highlighting outliers for small-molecule ligands, which contains information about any issues with chirality when compared with the standard wwPDB Chemical Component Dictionary (CCD; Westbrook et al, 2015), outliers in geometry as highlighted using Mogul analysis, close contacts and issues with experimental evidence: electron density in the case of X-ray crystallographic structures, as assessed by local ligand density fit (LLDF) analysis (for a detailed examination of ligand validation, see Smart et al, 2018). The residue-level details concerning outliers are provided in section 3 of the VR, which contains a residue-level plot for each polymeric chain.…”
Section: Introductionmentioning
confidence: 99%