2NBQ:
reference: Nuclear Magnetic Resonance Structure of the APOBEC3B Catalytic Domain: Structural Basis for Substrate Binding and DNA Deaminase Activity., Byeon IJ, Byeon CH, Wu T, Mitra M, Singer D, Levin JG, Gronenborn AM, Biochemistry. 2016 May 31;55(21):2944-59. doi: 10.1021/acs.biochem.6b00382. Epub , 2016 May 19. PMID: 27163633

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