4KI2:
reference: Crystallographic analysis of an RNA polymerase sigma-subunit fragment complexed with -10 promoter element ssDNA: quadruplex formation as a possible tool for engineering crystal contacts in protein-ssDNA complexes., Feklistov A, Darst SA, Acta Crystallogr Sect F Struct Biol Cryst Commun. 2013 Sep;69(Pt 9):950-5. doi:, 10.1107/S1744309113020368. Epub 2013 Aug 19. PMID: 23989139

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