Nature Chemical Biology 2, 39–46 (2006); published online 20 November 2005; corrected after print 7 March 2006.

In the version of this article initially published online, two labels in Figure 3a are incorrect. The label in the square below the arrow for step 2 should read 'Cdc42 GTP' instead of 'Cdc42 GDP', and 'PI' in step 4 should be 'Pi'. These errors have been corrected in the PDF version of the article. The corrected figure is below.