Nat. Chem. Biol. 12, 1065–1074 (2016); published online 17 October 2016; corrected after print 15 May 2017

In the version of this article initially published, two chemical compounds in Figure 5c were incorrectly drawn as protonated secondary amines instead of tertiary amines. The error has been corrected in the HTML and PDF versions of the article.