1UL3:
reference: The structures of the PII proteins from the cyanobacteria Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803., Xu Y, Carr PD, Clancy P, Garcia-Dominguez M, Forchhammer K, Florencio F, Vasudevan SG, Tandeau de Marsac N, Ollis DL, Acta Crystallogr D Biol Crystallogr 2003 Dec;59(Pt 12):2183-90. PMID: 14646076

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