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Specific loop modifications of the thrombin‐binding aptamer trigger the formation of parallel structures
Author(s) -
Aviñó Anna,
Portella Guillem,
Ferreira Ruben,
Gargallo Raimundo,
Mazzini Stefania,
Gabelica Valérie,
Orozco Modesto,
Eritja Ramon
Publication year - 2014
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.12670
Subject(s) - antiparallel (mathematics) , g quadruplex , intramolecular force , intermolecular force , duplex (building) , guanine , chemistry , aptamer , crystallography , nucleotide , dimer , stereochemistry , dna , biophysics , biology , molecule , biochemistry , genetics , physics , gene , organic chemistry , quantum mechanics , magnetic field
Guanine‐rich sequences show large structural variability, with folds ranging from duplex to triplex and quadruplex helices. Quadruplexes are polymorphic, and can show multiple stoichiometries, parallel and antiparallel strand alignments, and different topological arrangements. We analyze here the equilibrium between intramolecular antiparallel and intermolecular parallel G‐quadruplexes in the thrombin‐binding aptamer ( TBA ) sequence. Our theoretical and experimental studies demonstrate that an apparently simple modification at the loops of TBA induces a large change in the monomeric antiparallel structure of TBA to yield a parallel G‐quadruplex showing a novel T‐tetrad. The present results illustrate the extreme polymorphism of G‐quadruplexes and the ease with which their conformation in solution can be manipulated by nucleotide modification.