An efficient method for solving RNA structures: MAD phasing by replacing magnesium with zinc.
The structure of a 46-nucleotide RNA complex has been successfully solved using multi-wavelength anomalous dispersion (MAD) at the zinc K edge. Taking advantage of the eight magnesium-binding sites, it has been shown that for five of them magnesium could be replaced by zinc. This resulted in an excellent 2.0 A MAD electron-density map. Zinc, in common with some other transition metals, is able to replace magnesium in RNA structures, but zinc has the advantage of its K edge being ideally located at 1.284 A. As most RNA molecules contain magnesium-binding sites, it is suggested that this method could be a valuable alternative to the use of bromo derivatives of bases, which is limited to chemically synthesizable and thus rather short RNA sequences.
Ennifar
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UPR 9002 du CNRS, IBMC, 15 Rue R. Descartes, 67084 Strasbourg CEDEX, France.
Walter
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Dumas
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D018360:Crystallography, X-Ray / Q000379:methods; D004583:Electrons; D008274:Magnesium; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry*; D015032:Zinc
D012313:RNA; D008274:Magnesium; D015032:Zinc