Left: A guanine tetrad featuring a central cation Right: Three guanine tetrads contributing to the structure of a G-quadruplex
In molecular biology, a guanine tetrad (also known as a G-tetrad or G-quartet) is a structure composed of four
guanine bases in a
square planar array.[1][2] They most prominently contribute to the structure of
G-quadruplexes, where their hydrogen bonding stabilizes the structure.[3][4] Usually, there are at least two guanine tetrads in a G-quadruplex, and they often feature
Hoogsteen-style hydrogen bonding.[1]
Guanine tetrads are formed by sequences rich in guanine, such as GGGGC.[5] They may also play a role in the
dimerization of
non-endogenous RNAs to facilitate the replication of some viruses.[5] Guanine tetrads dimerize through their 5' ends since it is more
energetically favorable.[6]
They can be stabilized by central
cations, such as lithium, sodium, potassium,
rubidium, or
caesium.[7][8] However, they still form a variety of different structures.[1] Guanine tetrads are not always stable, but the
sugar-phosphate backbone of DNA can assist in stability of the guanine tetrads themselves.[1] Guanine tetrads are more stable when stacked, as
intermolecular forces between each layers help stabilize them.[9]
^Azargun, Mohammad; Fridgen, Travis D. (2015-09-30). "Guanine tetrads: an IRMPD spectroscopy, energy resolved SORI-CID, and computational study of M(9-ethylguanine)4+ (M = Li, Na, K, Rb, Cs) in the gas phase". Physical Chemistry Chemical Physics. 17 (39): 25778–25785.
Bibcode:
2015PCCP...1725778A.
doi:
10.1039/C5CP00580A.
ISSN1463-9084.
PMID25845669.
^Fancui, Meng; Weiren, Xu; Chengbu, Liu (May 2004). "Theoretical study of incorporating 6-thioguanine into a guanine tetrad and their influence on the metal ion guanine tetrad". Chemical Physics Letters. 389 (4): 421–426.
Bibcode:
2004CPL...389..421M.
doi:
10.1016/j.cplett.2004.03.128.