2ZNI:
reference: Pyrrolysyl-tRNA synthetase-tRNA(Pyl) structure reveals the molecular basis of orthogonality., Nozawa K, O'Donoghue P, Gundllapalli S, Araiso Y, Ishitani R, Umehara T, Soll D, Nureki O, Nature. 2009 Feb 26;457(7233):1163-7. Epub 2008 Dec 31. PMID: 19118381

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