Figure 1

Structure of a G quartet. In this schematic representation, the sequence of sc1 RNA is used to illustrate the three-dimensional structure of a Gquartet; sc1 is one of a series of six random RNAs specifically bound by FMRP [4]. Four guanines form hydrogen bonds with each other in a symmetrical square planar arrangement. The G-quartet structure is stabilized by cations such as K⁺.