Nat. Cell Biol. 13, 117–123 (2011); published online 23 January 2011; corrected after print 28 January 2011;

In the version of this article initially published online and in print, the values for kout and kin in table 1 were incorrect. The correct values are (×10− 3 s−1). This error has been corrected in both the HTML and PDF versions of the article.