MOTS-C — Mitochondrial Peptide in Metabolic Research

Disclaimer: The following article is for educational and informational purposes only. The substances described are intended for research and laboratory use only. This does not constitute medical advice or an encouragement to use in humans or animals.

Introduction

MOTS-C (Mitochondrial Open Reading Frame of the Twelve S rRNA Type-C) is a 16-amino acid mitochondrial peptide discovered in 2015 by Changhan Lee’s team at the University of Southern California. It is the first described peptide encoded by mitochondrial DNA (mtDNA) that acts as a signaling factor outside the mitochondria — in the cytoplasm and cell nucleus.

The discovery of MOTS-C transformed the perception of mitochondria — from purely energy-producing organelles to active sources of signaling peptides that regulate whole-body metabolism. The gene encoding MOTS-C is located within the MT-RNR1 gene (12S rRNA) of mitochondrial DNA, making it part of a new class of peptides called Mitochondrial-Derived Peptides (MDPs).

Our store offers research-grade MOTS-C in lyophilized form (10 mg) with purity ≥98% HPLC. The second mitochondrial peptide in our catalog — SS-31 — works through a different mechanism (cardiolipin stabilization in the inner mitochondrial membrane).

Molecular Structure of MOTS-C

MOTS-C is a 16-amino acid peptide with the sequence MRWQEMGYIFYPRKLR and a molecular weight of ~2174.6 Da (CAS: 1627580-64-6). Several structural features distinguish it from other research peptides:

• Mitochondrial encoding — MOTS-C is encoded by the MT-RNR1 gene in mtDNA, not by nuclear DNA. It uses the mitochondrial genetic code, in which the AGA codon encodes a stop signal (in the nuclear code, it encodes arginine)
• Abundance of aromatic residues — the sequence contains tryptophan (W³), tyrosine (Y⁸, Y¹⁰), phenylalanine (F⁹, F¹¹), and proline (P¹²), giving the peptide a hydrophobic character and the ability to interact with lipid membranes
• Methionine residues (Met¹, Met⁶) — two methionines make MOTS-C susceptible to oxidative degradation, requiring careful storage
• C-terminal basic motif (RKLR) — the last four amino acids form a nuclear localization signal (NLS), enabling transport of the peptide to the cell nucleus

Mechanism of Action: AMPK Activation

The central mechanism of MOTS-C action is the activation of AMPK (AMP-activated Protein Kinase) — the master regulator of cellular energy homeostasis, often referred to as the cell’s „energy sensor.”

MOTS-C signaling cascade:

1. Folate pathway inhibition — MOTS-C inhibits the enzyme ATIC (5-aminoimidazole-4-carboxamide ribonucleotide transformylase/IMP cyclohydrolase) in the cytoplasmic de novo purine biosynthesis pathway
2. AICAR accumulation — blocking ATIC causes accumulation of the metabolite AICAR (5-aminoimidazole-4-carboxamide ribonucleotide), an endogenous AMPK activator
3. AMPK activation — AICAR mimics an increase in the AMP/ATP ratio, activating AMPK through phosphorylation of Thr172 on the α subunit
4. Metabolic effects — active AMPK triggers a cascade of catabolic processes: fatty acid β-oxidation, glucose uptake (GLUT4 translocation), mitochondrial biogenesis (PGC-1α), and autophagy

This mechanism — indirect AMPK activation through folate pathway inhibition — is unique to MOTS-C. Metformin, the most commonly used AMPK activator in research, acts by inhibiting Complex I of the respiratory chain, an entirely different pathway.

Nuclear Translocation and Epigenetic Regulation

One of the most surprising discoveries about MOTS-C is its ability to translocate to the cell nucleus in response to metabolic stress. Studies by Kim et al. (2018) demonstrated that under conditions of glucose or oxidative stress, MOTS-C moves from the cytoplasm to the nucleus, where it directly regulates gene expression.

In the nucleus, MOTS-C interacts with DNA at ARE (Antioxidant Response Elements) regions and modulates genes involved in the oxidative stress response, including genes of the NRF2 (Nuclear Factor Erythroid 2-Related Factor 2) pathway. This retrograde signaling — a mitochondrial peptide regulating nuclear gene transcription — represents a new paradigm of mito-nuclear communication.

The C-terminal RKLR motif serves as a nuclear localization signal (NLS), enabling transport through the nuclear pore complex. Mutations in this motif abolish nuclear translocation and significantly attenuate the metabolic effects of MOTS-C.

Research Areas

Glucose Homeostasis and Insulin Sensitivity

In the first publication describing MOTS-C (Lee et al., 2015), it was shown that administration of the peptide to mice on a high-fat diet prevented the development of insulin resistance and diet-induced obesity. The effect was dependent on AMPK activation and increased glucose uptake in skeletal muscle (GLUT4 translocation).

Subsequent studies confirmed that endogenous blood levels of MOTS-C correlate negatively with age and insulin resistance markers (HOMA-IR). In individuals with type 2 diabetes, reduced levels of circulating MOTS-C were observed compared to the control group.

Physical Performance and Muscle Metabolism

MOTS-C demonstrates particular affinity for skeletal muscle tissue — the body’s primary consumer of glucose and fatty acids. In mouse models, MOTS-C administration increased physical endurance and resistance to muscle fatigue. The mechanism involves:

• Activation of fatty acid β-oxidation in muscles (via AMPK → ACC → CPT1)
• Increased mitochondrial biogenesis (AMPK → PGC-1α → NRF1/2 → TFAM)
• Improved metabolic flexibility — the ability to switch between energy substrates (glucose vs fatty acids)

Interestingly, physical exercise itself increases MOTS-C expression in muscles and its release into circulation — suggesting a feedback loop between physical activity and mitochondrial signaling.

Aging and Longevity

Circulating MOTS-C levels decline with age — similar to other mitochondrial peptides (humanin). This decline correlates with the accumulation of mtDNA mutations, mitochondrial dysfunction, and age-related deterioration of metabolic homeostasis.

In epidemiological studies, a specific polymorphism of the MT-RNR1 gene (m.1382A>C), leading to a change in the MOTS-C sequence (K14Q), is significantly overrepresented in the population of Japanese men over 100 years of age. This observation suggests a link between MOTS-C variants and longevity, although the causal mechanism requires further investigation.

MOTS-C vs SS-31 — Two Approaches to Mitochondria

MOTS-C and SS-31 (Elamipretide) are two mitochondrial peptides available in our catalog, but their mechanisms are fundamentally different:

MOTS-C works „top-down” — it activates AMPK, which then stimulates mitochondrial biogenesis. SS-31 works „from within” — it stabilizes the inner mitochondrial membrane structure, optimizing the efficiency of the existing respiratory chain. These approaches are complementary.

Storage and Stability of MOTS-C

MOTS-C requires particular attention during storage due to the presence of two methionine residues (Met¹ and Met⁶) and a tryptophan residue (Trp³) — amino acids most susceptible to oxidation:

• Lyophilized form: store at ≤ -20°C in a tightly sealed vial, protected from UV light and moisture. Stability exceeds 24 months.
• After reconstitution: solution in bacteriostatic water should be stored at 2-8°C and used within 14 days. Do not freeze after reconstitution.
• Degradation: oxidation of Met¹/Met⁶ to methionine sulfoxides and photooxidation of Trp³ are the primary degradation pathways. Exposure to light and elevated temperature accelerate these processes.

For more on degradation mechanisms and peptide stability, see our knowledge base articles on peptide stability and storage best practices.

Frequently Asked Questions

What is MOTS-C?
MOTS-C (Mitochondrial Open Reading Frame of the Twelve S rRNA Type-C) is a 16-amino acid peptide encoded by mitochondrial DNA (MT-RNR1 gene). Discovered in 2015, it is the first described mitochondrial peptide that acts as a systemic metabolic regulator. Molecular weight ~2174.6 Da, CAS: 1627580-64-6.

How does MOTS-C work?
MOTS-C activates AMPK — the cell’s master energy sensor — by inhibiting the enzyme ATIC in the purine biosynthesis pathway. Accumulation of the metabolite AICAR activates AMPK, which triggers fatty acid β-oxidation, glucose uptake, and mitochondrial biogenesis. Under stress conditions, MOTS-C translocates to the nucleus, where it regulates antioxidant response genes.

How does MOTS-C differ from SS-31?
Both are mitochondrial peptides, but they work differently. MOTS-C (16 aa, encoded by mtDNA) activates AMPK and stimulates the biogenesis of new mitochondria. SS-31 (4 aa, synthetic) binds cardiolipin in the inner mitochondrial membrane, optimizing the existing respiratory chain. These approaches are complementary.

Why do MOTS-C levels decline with age?
The decline in circulating MOTS-C correlates with the accumulation of mtDNA mutations and age-related mitochondrial dysfunction. Individuals over 60 show significantly lower MOTS-C levels than young adults. Interestingly, physical exercise increases MOTS-C expression in muscles.

How should MOTS-C be stored?
Store the lyophilized form at ≤ -20°C (stability >24 months). After reconstitution in bacteriostatic water, store at 2-8°C and use within 14 days. MOTS-C contains two methionines and a tryptophan susceptible to oxidation — protect from UV light.

Bibliography

1. Lee C et al. (2015). „The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance.” Cell Metab, 21(3):443-454. doi:10.1016/j.cmet.2015.02.009
2. Kim SJ et al. (2018). „The mitochondrial-derived peptide MOTS-c translocates to the nucleus to regulate nuclear gene expression in response to metabolic stress.” Cell Metab, 28(3):516-524. doi:10.1016/j.cmet.2018.06.008
3. Reynolds JC et al. (2021). „MOTS-c is an exercise-induced mitochondrial-encoded regulator of age-dependent physical decline and muscle homeostasis.” Nat Commun, 12(1):470. doi:10.1038/s41467-020-20790-0
4. Fuku N et al. (2015). „The mitochondrial-derived peptide MOTS-c: a player in exceptional longevity?” Aging Cell, 14(6):921-923. doi:10.1111/acel.12389
5. Zempo H et al. (2021). „A pro-diabetogenic mtDNA polymorphism in the mitochondrial-derived peptide, MOTS-c.” Aging (Albany NY), 13(2):1692-1717. doi:10.18632/aging.202529
6. Kim KH, Son JM, Benayoun BA, Lee C (2018). „The Mitochondrial-Encoded Peptide MOTS-c Translocates to the Nucleus to Regulate Nuclear Gene Expression.” Cell Metab, 28(3):516-524.
7. Lee C, Kim KH, Cohen P (2016). „MOTS-c: A novel mitochondrial-derived peptide regulating muscle and fat metabolism.” Free Radic Biol Med, 100:182-187. doi:10.1016/j.freeradbiomed.2016.05.015