4ND6:
reference: Structural Basis of Improved Second-Generation 3-Nitro-tyrosine tRNA Synthetases., Cooley RB, Feldman JL, Driggers CM, Bundy TA, Stokes AL, Karplus PA, Mehl RA, Biochemistry. 2014 Apr 1;53(12):1916-24. doi: 10.1021/bi5001239. Epub 2014 Mar, 20. PMID: 24611875

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