3C1I:
reference: Substrate binding, deprotonation, and selectivity at the periplasmic entrance of the Escherichia coli ammonia channel AmtB., Javelle A, Lupo D, Ripoche P, Fulford T, Merrick M, Winkler FK, Proc Natl Acad Sci U S A. 2008 Apr 1;105(13):5040-5. Epub 2008 Mar 24. PMID: 18362341

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