NMR trial models: experiences with the colicin immunity protein Im7 and the p85α C-terminal SH2-peptide complex

• Published in: Acta crystallographica. Section D, Biological crystallography. Vol. 57; no. 10; pp. 1397 - 1404
• Main Authors: Pauptit, Richard A., Dennis, Caitríona A., Derbyshire, Dean J., Breeze, Alexander L., Weston, Simon A., Rowsell, Siân, Murshudov, Garib N.
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England Munksgaard International Publishers 01-10-2001
• Subjects: molecular replacement; NMR trial models; phosphatidylinositol 3-OH kinase
• ISSN: 1399-0047; 0907-4449; 1399-0047
• DOI: 10.1107/S0907444901012434

Two cases of successful molecular replacement using NMR trial models are presented. One is the crystal structure of the Escherichia coli colicin immunity protein Im7; the other is a heretofore unreported crystal structure of a specific PDGF receptor‐derived peptide complex of the carboxy‐terminal SH2 domain from the p85α subunit of human phosphatidylinositol 3‐OH kinase. In both cases, molecular replacement was non‐trivial. Success was achieved using trial models that consisted of an ensemble of NMR structures from which the more flexible portions had been excized. Use of maximum‐likelihood refinement proved critical to be able to refine the poor starting models. The challenges typical of the use of NMR trial models in molecular replacement are discussed.