4CTD:
reference: Structure-based engineering of a minimal porin reveals loop-independent channel closure., Grosse W, Psakis G, Mertins B, Reiss P, Windisch D, Brademann F, Burck J, Ulrich A, Koert U, Essen LO, Biochemistry. 2014 Jul 29;53(29):4826-38. doi: 10.1021/bi500660q. Epub 2014 Jul, 15. PMID: 24988371

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