• Structure of the Escherichia coli ProQ RNA-binding protein.

      Gonzalez, Grecia M; Hardwick, Steven W; Maslen, Sarah L; Skehel, J Mark; Holmqvist, Erik; Vogel, Jörg; Bateman, Alex; Luisi, Ben F; Broadhurst, R William; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-05)
      The protein ProQ has recently been identified as a global small noncoding RNA-binding protein in Salmonella, and a similar role is anticipated for its numerous homologs in divergent bacterial species. We report the solution structure of Escherichia coli ProQ, revealing an N-terminal FinO-like domain, a C-terminal domain that unexpectedly has a Tudor domain fold commonly found in eukaryotes, and an elongated bridging intradomain linker that is flexible but nonetheless incompressible. Structure-based sequence analysis suggests that the Tudor domain was acquired through horizontal gene transfer and gene fusion to the ancestral FinO-like domain. Through a combination of biochemical and biophysical approaches, we have mapped putative RNA-binding surfaces on all three domains of ProQ and modeled the protein's conformation in the apo and RNA-bound forms. Taken together, these data suggest how the FinO, Tudor, and linker domains of ProQ cooperate to recognize complex RNA structures and serve to promote RNA-mediated regulation.