(A) FMRP domain structure. The different motifs are indicated: NDF, NLS, NES, KH1 and KH2, and RGG stand for the N-terminal domain of FMRP, the nuclear localization signal, the nuclear export signal, the two K-homology (KH) domains, and the RGG motif, respectively. The sequence of RGG_P is shown in the inset. Four additional residues (in lower case) were added for cloning and purification purposes. (B) Far-UV CD spectra of RGG_P at pH 5 (black curve) and pH 7 (gray curve) and 20°C. (C) 1H-15N HSQC spectra of the peptide at pH 5 (top) and 7.4 (bottom). The spectra were recorded at 27°C using a 1.3-mM concentration of RGG_P. Partial assignment of the peptide resonances is indicated. The sidechain exchangeable protons of Arg, Gln, and Asn are indicated by (sc).
