ArgGlyGly

ArgGlyGly, often written as Arg-Gly-Gly or abbreviated RGG, is the three-amino-acid sequence consisting of arginine (Arg), glycine (Gly), and glycine. It is a short motif that can occur as part of larger protein regions or as a repeating unit within glycine-rich segments. In proteins, the one-letter code for this sequence is RGG.

Chemical and structural properties: Arginine carries a positive charge at physiological pH, while glycine is the smallest amino acid and imparts flexibility to peptide chains. The combination in ArgGlyGly can contribute to conformational adaptability in flexible regions of proteins and to electrostatic interactions with negatively charged molecules such as nucleic acids. When found in repeats (RGG motifs), this region tends to be highly glycine-rich and can adopt various conformations depending on context and modifications.

Biological context and function: The RGG motif is a well-known feature of many RNA-binding proteins, including certain heterogeneous nuclear ribonucleoproteins and the Fragile X mental retardation protein (FMRP). The arginine-rich portion of these motifs facilitates binding to RNA, while surrounding glycines provide flexibility. Post-translational modifications, particularly arginine methylation by protein arginine methyltransferases (PRMTs), can modulate RNA binding, protein-protein interactions, localization, and phase separation behavior in cells. RGG-containing regions are also associated with the formation of ribonucleoprotein granules and other biomolecular condensates.

Applications and research notes: In basic research, ArgGlyGly-containing peptides are used to study RNA binding, protein interactions, and the biophysical properties of glycine-rich regions. Synthetic variants help probe how sequence context and methylation state influence function. ArgGlyGly itself does not denote a standalone bioactive compound but serves as a common motif within larger protein domains.