Nat. Struct. Biol. 10, 718–724 (2003).

A mistake was introduced when the electronic document of this manuscript was being converted for production. The mistake is in the peptide sequence corresponding to the 19 residues at the C terminus of p27Kip1 page 723, second column, line 2). The correct sequence should be: NAGSVEQ(pT)PKKPGLRRRQT. We apologize for any inconvenience this may have caused.