4A9V:
reference: A complex iron-calcium cofactor catalyzing phosphotransfer chemistry., Yong SC, Roversi P, Lillington J, Rodriguez F, Krehenbrink M, Zeldin OB, Garman EF, Lea SM, Berks BC, Science. 2014 Sep 5;345(6201):1170-3. doi: 10.1126/science.1254237. PMID: 25190793

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