Monellin, A chain (IPR000828)

Short name: Monellin_A

Overlapping homologous superfamilies

Family relationships

  • Monellin (IPR015283)
    • Monellin, A chain (IPR000828)


Monellin is an intensely sweet-tasting protein derived from African berries. The protein has a very high specificity for the sweet receptors, making it ~100,000 times sweeter than sugar on a molar basis and several thousand times sweeter on a weight basis. Like the sweet-tasting protein thaumatin, it neither contains carbohydrates nor modified amino acids. Although there is no sequence similarity between the proteins, antibodies for thaumatin compete for monellin (and other sweet compounds, but not for chemically modified non-sweet monellin) and vice versa [PMID: 3614382]. It is thought that native conformations are important for the sweet taste. Monellin is a heterodimer, comprising an A chain of 44 amino acid residues, and a B chain of 50 residues. The individual subunits are not sweet, nor do they block the sweet sensation of sucrose or monellin. However, blocking the single SH of monellin abolishes its sweetness, as does reaction of its methionyl residue with CNBr [PMID: 1368575]. The cysteinyl and methionyl residues are adjacent, and it has therefore been suggested that this part of the molecule is essential for its sweetness [PMID: 4107]. The structure of monellin belongs to the alpha/beta class, a 5-stranded beta-sheet sequestering a single alpha-helix. The A chain contributes 3 strands to the sheet.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.