1YF2:
reference: Crystal structure of DNA sequence specificity subunit of a type I restriction-modification enzyme and its functional implications., Kim JS, Degiovanni A, Jancarik J, Adams PD, Yokota H, Kim R, Kim SH, Proc Natl Acad Sci U S A 2005 Mar 1;102(9):3248-53. Epub 2005 Feb 22. PMID: 15728358

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