Nat. Struct. Mol. Biol. 19, 1059–1061 (2012); published online 6 November 2012; corrected after print 20 December 2012

In the version of this article initially published, in the lower part of Figure 2, the upper arrow connecting Cdc20 to the APC/C to form APC/CCdc20 pointed in the wrong direction. The error has been corrected in the HTML and PDF versions of the article.