DSSR-PyMOL cartoon-block schematics: PDB entry 2kow

PDB-id

2kow; DSSR-derived features in text and JSON formats

Class

DNA

Method

NMR

Summary

Structure of a two-g-tetrad basket-type intramolecular g-quadruplex formed by giardia telomeric repeat d(taggg)4 in k+ solution (with g18-to-ino substitution)

Reference

Hu L, Lim KW, Bouaziz S, Phan AT (2009): "Giardia Telomeric Sequence d(TAGGG)(4) Forms Two Intramolecular G-Quadruplexes in K(+) Solution: Effect of Loop Length and Sequence on the Folding Topology." J.Am.Chem.Soc., 131, 16824-16831. doi: 10.1021/ja905611c.

Abstract

Recently, it has been shown that in K(+) solution the human telomeric sequence d[TAGGG(TTAGGG)(3)] forms a (3 + 1) intramolecular G-quadruplex, while the Bombyx mori telomeric sequence d[TAGG(TTAGG)(3)], which differs from the human counterpart only by one G deletion in each repeat, forms a chair-type intramolecular G-quadruplex, indicating an effect of G-tract length on the folding topology of G-quadruplexes. To explore the effect of loop length and sequence on the folding topology of G-quadruplexes, here we examine the structure of the four-repeat Giardia telomeric sequence d[TAGGG(TAGGG)(3)], which differs from the human counterpart only by one T deletion within the non-G linker in each repeat. We show by NMR that this sequence forms two different intramolecular G-quadruplexes in K(+) solution. The first one is a novel basket-type antiparallel-stranded G-quadruplex containing two G-tetrads, a G x (A-G) triad, and two A x T base pairs; the three loops are consecutively edgewise-diagonal-edgewise. The second one is a propeller-type parallel-stranded G-quadruplex involving three G-tetrads; the three loops are all double-chain-reversal. Recurrence of several structural elements in the observed structures suggests a "cut and paste" principle for the design and prediction of G-quadruplex topologies, for which different elements could be extracted from one G-quadruplex and inserted into another.