Summary information and primary citation

PDB-id
4pzq; DSSR-derived features in text and JSON formats
Class
DNA
Method
X-ray (2.24 Å)
Summary
Crystal structure of ccg DNA repeats
Reference
Chen YW, Jhan CR, Neidle S, Hou MH (2014): "Structural basis for the identification of an i-motif tetraplex core with a parallel-duplex junction as a structural motif in CCG triplet repeats." Angew.Chem.Int.Ed.Engl., 53, 10682-10686. doi: 10.1002/anie.201405637.
Abstract
CCG triplet repeats can fold into tetraplex structures, which are associated with the expansion of (CCG)n trinucleotide sequences in certain neurological diseases. These structures are stabilized by intertwining i-motifs. However, the structural basis for tetraplex i-motif formation in CCG triplet repeats remains largely unknown. We report the first crystal structure of a CCG-repeat sequence, which shows that two dT(CCG)3 A strands can associate to form a tetraplex structure with an i-motif core containing four C:C(+) pairs flanked by two G:G homopurine base pairs as a structural motif. The tetraplex core is attached to a short parallel-stranded duplex. Each hairpin itself contains a central CCG loop in which the nucleotides are flipped out and stabilized by stacking interactions. The helical twists between adjacent cytosine residues of this structure in the i-motif core have an average value of 30°, which is greater than those previously reported for i-motif structures.

Cartoon-block schematics in six views (download the tarball)

PyMOL session file Download PDB file View in 3Dmol.js