3NQS:
reference: Nitric-oxide synthase forms N-NO-pterin and S-NO-cys: implications for activity, allostery, and regulation., Rosenfeld RJ, Bonaventura J, Szymczyna BR, MacCoss MJ, Arvai AS, Yates JR 3rd, Tainer JA, Getzoff ED, J Biol Chem. 2010 Oct 8;285(41):31581-9. Epub 2010 Jul 21. PMID: 20659888

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