1U9Y:
reference: Novel class III phosphoribosyl diphosphate synthase: structure and properties of the tetrameric, phosphate-activated, non-allosterically inhibited enzyme from Methanocaldococcus jannaschii., Kadziola A, Jepsen CH, Johansson E, McGuire J, Larsen S, Hove-Jensen B, J Mol Biol. 2005 Dec 9;354(4):815-28. Epub 2005 Oct 18. PMID: 16288921

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