WWamides
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WWamides, biologically active 7-peptide amides originally isolated from ganglia of the Africa snail Achatina fulica. The name is related to the both terminal Trp (W) residues. WWamide-1, H-Trp-Lys-Glu-Met-Ser-Val-Trp-NH2, shows inhibitory activity on a central neuron of the snail. Furthermore, it exhibits peripheral modulatory effects on muscular contractions in various tissues of the snail and other mollusks. WWamide-2 corresponds to [Arg2] WWamide-1 and WWamide-3 to [Gln3] WWamide-1, respectively.
Structural Characteristics
Kinetic studies show that structure of WWamides similar to the natural secondary structure is formed in the folded transition protein ring, but the order of the main chain is low at other positions in the sequence. Its amino acid sequence is H-Trp-Lys-Glu-Met-Ser-Val-Trp-NH2. The WWamide-2 sequence was H Trp Arg GluMetSer TrpNH 2, the WWamide3 sequence was H Trp LysGlngel TrpNH 2, and the sequence was H-Trp-Arg-Glu-Met-Ser-Val-Trp-NH2.
Mode of Action
The synthetic WWamide-1 can inhibit the central neurons of snails and regulate the muscle contraction of different tissues of snails and other molluscs. It has been considered that amide to E-olefine (A-to-O) mutation is an ideal peptide bond disturbance. The A-to-O mutation in the protein eliminates a hydrogen bond donor (NH) and a hydrogen bond receptor (CO), without causing electrostatic rejection. However, this strategy is rarely implemented because of the difficulty of stereotactic synthesis of olefine isotopes and their integration into proteins. A-to-O and A-to-E mutations were used to disturb the Phe22-Phe23 amide bond in the Pin WW domain. The energy comparison between ester mutants and E-olefine mutants can quantify the rejection O-O interaction caused by A-to-E mutation. And the energy of H bond is established. Fumihiro M et al found a tachykinin-like peptide (ThTK), two kinds of FRFamides and a kind of WWamide in snails in 2006. ThTK could induce contraction of esophagus, prostate and capsule gland, while FRFamide and WWamide could inhibit the contraction of esophagus, prostate and capsule gland. The distribution of these peptides in the central nervous system was confirmed by immunostaining with specific antibodies.
References
- Minakata, H., Ikeda, T., Muneoka, Y., Kobayashi, M., & Nomoto, K. (1993). WWamide‐1,‐2 and‐3: novel neuromodulatory peptides isolated from ganglia of the African giant snail, Achatina fulica. FEBS letters, 323(1-2), 104-108.
- Gao, J., & Kelly, J. W. (2008). Toward quantification of protein backbone–backbone hydrogen bonding energies: An energetic analysis of an amide‐to‐ester mutation in an α‐helix within a protein. Protein Science, 17(6), 1096-1101.
