MOTS-c

MOTS-c is a 16-residue peptide encoded not in the nuclear genome but within the mitochondrial genome — specifically in a short open reading frame inside the 12S ribosomal RNA gene. It belongs to the small class of mitochondrial-derived peptides, molecules whose coding sequence sits on mitochondrial DNA and which are read using the mitochondrial genetic code. That origin is the single most interesting fact about it as a research reagent, and it is what places the peptide in a category of its own.

Identity and classification

MOTS-c stands for “mitochondrial open reading frame of the 12S rRNA type-c”. The acronym is rendered inconsistently across catalogues — some expand it with “tRNA” rather than “rRNA”. The original characterisation of the peptide places it in the 12S ribosomal RNA gene, and rRNA is the correct expansion.

No receptor or molecular target is assigned to MOTS-c in reference-supplier catalogue classification. Unlike the melanocortin or GHRH peptides elsewhere in this library, it is not catalogued as a ligand for any named receptor, and we make no claim about a target. It is supplied and characterised as a sequence-defined synthetic peptide.

Structure

The sequence is Met-Arg-Trp-Gln-Glu-Met-Gly-Tyr-Ile-Phe-Tyr-Pro-Arg-Lys-Leu-Arg, written in single-letter code as MRWQEMGYIFYPRKLR. All sixteen residues are standard L-amino acids. There are no D-amino acids, no non-natural residues, no cyclisation and no C-terminal amidation — both termini are free.

A point that causes confusion when reading the molecular formula: the two sulfur atoms in C₁₀₁H₁₅₂N₂₈O₂₂S₂ are the two methionine residues at positions 1 and 6. MOTS-c contains no cysteine and therefore no disulfide bond. A specification describing a disulfide bridge in this peptide is describing something else.

The composition is unusually aromatic for a peptide of this length — one tryptophan, two tyrosines and one phenylalanine — which is convenient analytically, as discussed below.

Specification and characterisation

The characterisation set appropriate to this peptide is the standard synthetic-peptide panel, with two features specific to its composition:

• RP-HPLC purity. Detection at 214 nm reports the amide backbone. Because MOTS-c carries Trp and two Tyr residues, a second channel at 280 nm is genuinely informative here rather than merely conventional — a peak with backbone absorbance but no aromatic absorbance is not this peptide.
• Mass confirmation. ESI-MS or MALDI-TOF against the average mass of 2174.6. At this mass a multiply-charged ESI envelope is the practical route.
• Methionine oxidation. Two methionines mean two sites where a +16 Da adduct can appear. A peak at approximately 2190.6, or a shoulder eluting slightly earlier than the main peak on reverse phase, is the oxidised sulfoxide. This is the most likely degradation product and the one worth checking on receipt of an older lot.
• Net peptide content. Amino acid analysis or nitrogen determination establishes how much of the vial mass is peptide rather than counter-ion and residual water. With four basic residues — three arginines and a lysine — the acetate or trifluoroacetate burden on this peptide is not trivial.
• Counter-ion identity. Acetate and TFA salts behave differently and TFA is spectroscopically visible; ion chromatography distinguishes them.
• Water content. Karl Fischer titration on a lyophilised solid.

Handling and stability

Store the sealed vial at 2–8 °C, dry and protected from light. The two methionine residues make oxidation the dominant chemical degradation pathway, so minimising headspace oxygen and avoiding repeated warming of the vial matter more here than for a peptide without sulfur.

Allow the vial to reach room temperature in a desiccator before opening. Lyophilised peptides are hygroscopic and cold glass condenses atmospheric moisture, which is drawn into the cake the moment the seal is broken.

The peptide is water-soluble. As with any peptide carrying oxidisable residues, prepared solutions are markedly less stable than the dry solid.

Related compounds in this library

MOTS-c has no close structural relative among the other compounds we supply. It is grouped under mitochondrial research alongside SS-31, but the two are unrelated chemically — SS-31 is a four-residue aromatic-cationic peptide carrying a D-amino acid and a non-standard dimethyltyrosine, and shares neither sequence nor structural motif with MOTS-c. The grouping is thematic, not chemical.

References

Chemical, specification and analytical sources. This list is deliberately limited to chemistry and analytical references.

• Chemsrc, CAS 1627580-64-6 — formula, molecular weight, registry data
• ChemicalBook, MOTS-c product property record — formula and mass, independent confirmation
• American Peptides, MOTS-c Safety Data Sheet — molecular weight, sequence, handling
• Bachem, Handling and Storage Guidelines for Peptides — hygroscopicity, desiccator equilibration, oxidation-sensitive residues

Cosmic Aminos supplies this material as a laboratory reagent for in-vitro research use only. It is not a drug, food, cosmetic or dietary supplement, is not approved by the Food and Drug Administration for any use, and is not for human or veterinary consumption. No dosing, administration or preparation guidance is provided.