PMID: 11567151
Pauptit RA, Dennis CA, Derbyshire DJ, Breeze AL, Weston SA, Rowsell S, Murshudov GN
NMR trial models: experiences with the colicin immunity protein Im7 and the p85alpha C-terminal SH2-peptide complex.
Acta Crystallogr D Biol Crystallogr. 2001 Oct;57(Pt 10):1397-404. Epub, 2001 Sep 21.
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 p85alpha 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 excised. 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.