SELENIUM DERIVATIZATION OF NUCLEIC ACIDS FOR X-RAY CRYSTALLOGRAPHY VIA MAD

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. X-ray crystallography is a powerful tool for structure determination of RNA structure, RNA-protein and DNA-protein complexes with high resolution. Derivatization with heavy atoms for phase determination, a long-standing problem in X-ray crystallography, however, has largely slowed down structural determination of nucleic acids with novel folds. One approach to facilitate the structure determination is to label nucleic acids with covalently linked heavy atoms, which enable phase and structure determination. We have developed a novel strategy to derivatize RNA and DNA by replacing oxygen with selenium, and this principle has been demonstrated by X-ray crystallography using MAD phasing method. We are derivatizing DNA and catalytic and binding RNA sequences with novel folds, via chemical and enzymatic synthesis, for X-ray crystallographic studies of nucleic acids and their protein complexes.