. Author manuscript; available in PMC: 2020 Jan 12.
Published in final edited form as: J Mol Biol. 2019 May 17;431(15):2821–2834. doi: 10.1016/j.jmb.2019.04.048
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).