4RUL:
reference: Structural basis for suppression of hypernegative DNA supercoiling by E. coli topoisomerase I., Tan K, Zhou Q, Cheng B, Zhang Z, Joachimiak A, Tse-Dinh YC, Nucleic Acids Res. 2015 Dec 15;43(22):11031-46. doi: 10.1093/nar/gkv1073. Epub, 2015 Oct 20. PMID: 26490962

This OCA Structure page
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