. Author manuscript; available in PMC: 2021 Apr 30.
Published in final edited form as: Nat Chem Biol. 2020 Oct 5;17(2):178–186. doi: 10.1038/s41589-020-00657-7
Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:http://www.nature.com/authors/editorial_policies/license.html#terms