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Structure of a G-quadruplex. Left: a G-tetrad. Right: an intramolecular G4 complex. [1]: fig1 In molecular biology, G-quadruplex secondary structures (G4) are formed in nucleic acids by sequences that are rich in guanine. [2] They are helical in shape and contain guanine tetrads that can form from one, [3] two [4] or four strands. [5]
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.
In the core of G-quadruplex motif, two G-tetrad planes are formed by G5-G7-G12-G16 and G8-G11-G17-G20. The upper plane (G5-G7-G12-G16) is not a typical G-tetrad with the chain topology of anti-syn-anti-syn alternation. Instead, three guanines (G5, G7 and G16) adopt syn conformation, and only one guanine (G12) adopts anti conformation ...
Hoogsteen pointed out that if the alternative hydrogen-bonding patterns were present in DNA, then the double helix would have to assume a quite different shape. Hoogsteen base pairs are observed in alternative structures such as the four-stranded G-quadruplex structures that form in DNA and RNA.
The quadruplex can repeat several times consecutively, producing an immensely stable structure. The unique structure of quadruplex regions in RNA may serve different functions in a biological system. Two important functions are the binding potential with ligands or proteins, and its ability to stabilize the whole tertiary structure of DNA or RNA.
The resulting square planar structure is known as a guanine tetrad (also known as a G-tetrad or G-quartet) and when two or more guanine tetrads stack on top of each other, they form a G-quadruplex. These complex structures have been shown help to modulate telomere length through inhibition telomerase's ability to add tandem TTAGGG repeats ...
G-quadruplex G-quadruplex secondary structures (G4) are formed in nucleic acids by sequences that are rich in guanine. [4] They are helical in shape and contain guanine tetrads that can form from one, [5] two [6] or four strands. [7] D-loop
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