A NMR guided approach for CsrA-RNA crystallization.

Structure determination of protein-nucleic acid complexes remains a challenging task. Here we present a simple method for generating crystals of a CsrA-nucleic acid complex, guided entirely by results from nuclear magnetic resonances spectroscopy (NMR) spectroscopy. Using a construct that lacks thirteen non-essential C-terminal residues, efficient binding to DNA could be demonstrated. One CsrA dimer interacts with two DNA oligonucleotides, similar to previous findings with RNA. Furthermore, the NMR study of the CsrA-DNA complex was the basis for successfully homing in on conditions that were suitable for obtaining crystals of the CsrA-DNA complex. Our results may be useful for those cases where RNA in protein-nucleic acid complexes may be replaced by DNA.