Nat. Chem. Biol. 13, 551–557 (2017); published online 20 March 2017; corrected after print 4 April 2017 and 23 August 2017

In the version of this article initially published, the trace shown in Figure 4b was mislabeled as the RNA VqmR instead of the protein VqmA. The error has been corrected in the HTML and PDF versions of the article.