2IX2:
reference: Structure of the heterotrimeric PCNA from Sulfolobus solfataricus., Williams GJ, Johnson K, Rudolf J, McMahon SA, Carter L, Oke M, Liu H, Taylor GL, White MF, Naismith JH, Acta Crystallogr Sect F Struct Biol Cryst Commun. 2006 Oct 1;62(Pt, 10):944-8. Epub 2006 Sep 19. PMID: 17012780

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