A three-dimensional arrangement of guanine molecules which explains the interactions occurring within DNA strands that contain repeating units rich in guanine, such as telomeric repeats. One, two, or four DNA strands can fold into a compact unit containing a planar array of four guanines, as shown below. Each guanine serves both as a proton donor and acceptor with its neighbors, and so the quartet is held together by eight hydrogen bonds. The quartets can stack one above another. This stacking is facilitated by axially located monovalent cations. For example, Na+ fits exactly in the central cavity, and the slightly larger potassium ion can fit by binding in the cavity between adjacent quartets. See Chronology, 1989, Williamson, Raghuraman, and Czech; hydrogen bond, telomere.
Guanine quartet model
Subjects: Genetics and Genomics.