. Author manuscript; available in PMC: 2016 Mar 27.
Published in final edited form as: J Mol Biol. 2015 Jan 15;427(6 0 0):1278–1290. doi: 10.1016/j.jmb.2015.01.004
© 2015 Published by Elsevier Ltd.
This manuscript version is made available under the CC BY-NC-ND 4.0 license.