Mitochondrial-Derived Peptides: MOTS-c, Humanin and the SHLPs
Short peptides encoded in the mitochondrial genome, from reading frames nobody had annotated. A research area barely a decade old.
For most of the history of molecular biology, the mitochondrial genome was understood as encoding thirteen proteins, all components of the respiratory chain. The discovery that it also encodes short bioactive peptides — from reading frames nobody had annotated — opened a research area that is still young.
What a mitochondrial-derived peptide is
Mitochondria carry their own circular genome, a legacy of the endosymbiotic bacterium they descend from. Within the ribosomal RNA genes of that genome are small open reading frames that were not originally annotated as genes. Peptides translated from them are mitochondrial-derived peptides, or MDPs.
The known members:
| Peptide | Length | Encoded within |
|---|---|---|
| Humanin | 24 residues | 16S rRNA gene |
| MOTS-c | 16 residues | 12S rRNA gene |
| SHLP1–6 | 20–38 residues | 16S rRNA gene |
Humanin was identified first, in 2001, from surviving neurons in Alzheimer’s brain tissue. MOTS-c followed in 2015 — the name stands for mitochondrial open reading frame of the twelve S rRNA type-c. The SHLPs (small humanin-like peptides) were described alongside it.
Why the discovery mattered
Two reasons beyond the peptides themselves.
First, it changed the picture of mitochondrial signalling. The organelle had been understood as receiving instructions from the nucleus; MDPs describe a route in the other direction — retrograde signalling from mitochondrion to nucleus. MOTS-c in particular has been reported to translocate to the nucleus under metabolic stress and influence gene expression.
Second, it suggested that small open reading frames dismissed as noise across many genomes might encode functional peptides. That is now an active field in its own right.
What the literature reports
MOTS-c is described in relation to metabolic regulation, with reported effects on AMPK signalling and the folate–methionine cycle. Work in exercise physiology and in ageing models appears repeatedly.
Humanin is described mainly in cytoprotection and neuronal survival contexts, which reflects the circumstances of its discovery.
Two caveats belong with any summary of this area. The field is roughly a decade old for MOTS-c and two for humanin, so replication is thinner than for long-established peptides. And a substantial share of the work is in cell and rodent models — a normal stage for a young field, and a reason to read claims about translation carefully.
Analytical notes
At 16 residues, MOTS-c sits in a manageable range for solid-phase synthesis: enough steps that deletion sequences are a genuine impurity class, few enough that a good chromatogram resolves them.
Two sequence features are worth knowing:
- Methionine content. MOTS-c contains methionine, which oxidises to the sulfoxide with a +16 Da mass shift. This is one of the most common findings on a certificate for this compound and is a reason to minimise headspace and check the observed mass carefully.
- No cysteine, so no disulfide to form, scramble or reduce.
Standard handling applies otherwise: sealed lyophilised storage, equilibration to room temperature before opening, gentle reconstitution without shaking, refrigeration after reconstitution with use inside roughly 28 to 30 days.
Our MOTS-c article covers that compound in detail, and the certificate guide covers what the analytics should show.
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