Scientific Reports 3, Article number: 1302 (2013); Published: 18 February 2013; Updated: 08 April 2013

Due to a typesetting error, the reference to the Protein Data Bank entry was omitted in the original Article. This reference appears below.

Data deposition: Coordinates and structure factors have been deposited in the Protein Data Bank, www.pdb.org, under the accession code 4HIX.