Summary information and primary citation

PDB-id
6mc3; DSSR-derived features in text and JSON formats
Class
DNA
Method
X-ray (1.57 Å)
Summary
Crystal structure of a tetrameric DNA fold-back quadruplex
Reference
Chu B, Zhang D, Hwang W, Paukstelis PJ (2018): "Crystal Structure of a Tetrameric DNA Fold-Back Quadruplex." J. Am. Chem. Soc., 140, 16291-16298. doi: 10.1021/jacs.8b10153.
Abstract
DNA can adopt many structures beyond the Watson-Crick duplex. However, the bounds of DNA structural diversity and how these structures might regulate biological processes is only beginning to be understood. Here, we describe the 1.05 Å resolution crystal structure of a DNA oligonucleotide that self-associates to form a non-G-quadruplex fold-back structure. Distinct from previously described fold-back quadruplexes, two fold-back dimers interact through non-canonical and Watson-Crick interactions to form a tetrameric assembly. These interactions include a hexad base pairing arrangement from two C-G-G base triples. The assembly is dependent on divalent cations and the interface between the dimeric units creates a cavity in which a cation resides. This structure provides new sequence and structural contexts for the formation of fold-back quadruplexes, further highlighting the potential biological importance of this type of non-canonical DNA structure. This structure may also serve as the basis for designing new types of DNA nanoarchitectures or cation sensors based on the strong divalent cation dependence.

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