1UJW:
reference: The structure of BtuB with bound colicin E3 R-domain implies a translocon., Kurisu G, Zakharov SD, Zhalnina MV, Bano S, Eroukova VY, Rokitskaya TI, Antonenko YN, Wiener MC, Cramer WA, Nat Struct Biol 2003 Nov;10(11):948-54. Epub 2003 Oct 5. PMID: 14528295

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