A general method for phasing novel complex RNA crystal structures without heavy-atom derivatives
✍ Scribed by Robertson, Michael P. ;Scott, William G.
- Book ID
- 104478403
- Publisher
- International Union of Crystallography
- Year
- 2008
- Tongue
- English
- Weight
- 924 KB
- Volume
- 64
- Category
- Article
- ISSN
- 0907-4449
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✦ Synopsis
The crystallographic phase problem [Muirhead & Perutz (1963), Nature (London), 199, 633-638] remains the single major impediment to obtaining a three-dimensional structure of a macromolecule once suitable crystals have been obtained. Recently, it was found that it was possible to solve the structure of a 142-nucleotide L1 ligase ribozyme heterodimer that possesses no noncrystallographic symmetry without heavy-atom derivatives, anomalous scattering atoms or other modifications and without a model of the tertiary structure of the ribozyme [Robertson & Scott (2007), Science, 315, 1549-1553]. Using idealized known RNA secondary-structural fragments such as A-form helices and GNRA tetraloops in an iterative molecular-replacement procedure, it was possible to obtain an estimated phase set that, when subjected to solvent flattening, yielded an interpretable electron-density map with minimized model bias, allowing the tertiary structure of the ribozyme to be solved. This approach has also proven successful with other ribozymes, structured RNAs and RNAprotein complexes.