Unprecedented hour-long residence time of a cation in a left-handed G-quadruplex |
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Authors: | Fernaldo Richtia Winnerdy,Blaž Bakalar,Poulomi Das,Brahim Heddi,Adrien Marchand,Fré dé ric Rosu,Valé rie Gabelica,Anh Tuâ n Phan |
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Abstract: | Cations are critical for the folding and assembly of nucleic acids. In G-quadruplex structures, cations can bind between stacked G-tetrads and coordinate with negatively charged guanine carbonyl oxygens. They usually exchange between binding sites and with the bulk in solution with time constants ranging from sub-millisecond to seconds. Here we report the first observation of extremely long-lived K+ and NH4+ ions, with an exchange time constant on the order of an hour, when coordinated at the center of a left-handed G-quadruplex DNA. A single-base mutation, that switched one half of the structure from left- to right-handed conformation resulting in a right–left hybrid G-quadruplex, was shown to remove this long-lived behaviour of the central cation.An extremely long-lived cation has been detected in left-handed G-quadruplexes. |
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