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Double-lanthanide-binding tags for macromolecular crystallographic structure determination.

TitleDouble-lanthanide-binding tags for macromolecular crystallographic structure determination.
Publication TypeJournal Article
Year of Publication2007
AuthorsSilvaggi NR, Martin LJ, Schwalbe H, Imperiali B, Allen KN
JournalJ Am Chem Soc
Volume129
Pagination7114–7120
Date PublishedJun
Accession Number140
Abstract

A double-lanthanide-binding tag (dLBT), a small peptide sequence engineered to bind two lanthanide ions (e.g., Tb3+) with high affinity, was used to solve the phase problem for the structure determination of ubiquitin by the single-wavelength anomalous diffraction (SAD) method. Since the dLBT is comprised exclusively of encoded amino acids, the necessity for the incorporation of unnatural amino acids or chemical modification of the protein as a prerequisite for X-ray structure determination is eliminated. A construct encoding the dLBT as an N-terminal fusion with ubiquitin provides for facile expression and purification using standard methods. Phasing of the single-wavelength X-ray data (at 2.6 A resolution) using only the anomalous signal from the two tightly bound Tb3+ ions in the dLBT led to clear electron-density maps. Nearly 75% of the ubiquitin structure was built using automated model-building software without user intervention. It is anticipated that this technique will be broadly applicable, complementing existing macromolecular phasing methodologies. The dLBT should be particularly useful in cases where protein derivatization with heavy atoms proves to be problematic or synchrotron facilities are unavailable.

URLhttp://dx.doi.org/10.1021/ja070481n
DOI10.1021/ja070481n