1HOO:
reference: Refined crystal structures of guanine nucleotide complexes of adenylosuccinate synthetase from Escherichia coli., Poland BW, Hou Z, Bruns C, Fromm HJ, Honzatko RB, J Biol Chem 1996 Jun 28;271(26):15407-13. PMID: 8663109

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