Structural highlights
Publication Abstract from PubMedR.SwaI, a Type IIP restriction endonuclease, recognizes a palindromic eight base pair (bp) symmetric sequence, 5-ATTTAAAT-3, and cleaves that target at its center to generate blunt-ended DNA fragments. Here, we report three crystal structures of SwaI: unbound enzyme, a DNA-bound complex with calcium ions; and a DNA-bound, fully cleaved complex with magnesium ions. We compare these structures to two structurally similar 'PD-D/ExK' restriction endonucleases (EcoRV and HincII) that also generate blunt-ended products, and to a structurally distinct enzyme (the HNH endonuclease PacI) that also recognizes an 8-bp target site consisting solely of A:T base pairs. Binding by SwaI induces an extreme bend in the target sequence accompanied by un-pairing and re-ordering of its central A:T base pairs. This result is reminiscent of a more dramatic target deformation previously described for PacI, implying that long A:T-rich target sites might display structural or dynamic behaviors that play a significant role in endonuclease recognition and cleavage. DNA recognition by the SwaI restriction endonuclease involves unusual distortion of an 8 base pair A:T-rich target.,Shen BW, Heiter DF, Lunnen KD, Wilson GG, Stoddard BL Nucleic Acids Res. 2017 Feb 17;45(3):1516-1528. doi: 10.1093/nar/gkw1200. PMID:28180307[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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