October 14, 2026 · 2 min read
SS-31 (elamipretide): how a mitochondria-targeted tetrapeptide interacts with cardiolipin
A research overview of SS-31, also called elamipretide, covering its binding to cardiolipin, effects on mitochondrial membranes, and clinical program.
SS-31 is a four-amino-acid synthetic peptide, also known as elamipretide, MTP-131 and Bendavia. It comes from the Szeto-Schiller (SS) family of peptides, which were designed to accumulate in mitochondria. This is a summary of the published work on how it does that and what it does once it gets there.
The SS-31 sequence
Sequence: D-Arginine, 2',6'-Dimethyltyrosine, Lysine, Phenylalanine.
- Modified residue
- Positively charged
- Hydrophobic
- Length
- 4 residues, 2 of them modified
- Average mass
- 639.8 Da
- Formula
- C32H49N9O5
Why the membrane
Mitochondria make most of a cell's ATP using folded inner membranes called cristae. Those membranes are rich in cardiolipin, a negatively charged phospholipid that helps hold the cristae and the respiratory complexes together. When cardiolipin is damaged, for example by oxidation during ischemia, ATP production suffers. That makes it a recurring target in mitochondrial research.
Why cardiolipin matters
- 1
Cristae
Folded inner membranes where mitochondria make ATP.
- 2
Cardiolipin
A negatively charged lipid that helps hold cristae and respiratory complexes together.
- 3
Damage
Oxidation of cardiolipin, for example during ischemia, disrupts ATP production.
- 4
SS-31
Designed to accumulate in mitochondria and interact with cardiolipin.
Binding cardiolipin
A 2013 paper in the Journal of the American Society of Nephrology used a fluorescent analogue of SS-31 to show that it binds cardiolipin with high affinity. The complex inhibited the peroxidase activity of cytochrome c, which drives cardiolipin peroxidation, by protecting its heme iron. In a rat model of renal ischemia, pretreatment with SS-31 protected the cristae, prevented mitochondrial swelling, and let ATP recover quickly on reperfusion.
What the 2013 kidney study found
- 1
Binding
SS-31 binds cardiolipin with high affinity.
- 2
Peroxidase
The complex inhibits cytochrome c peroxidase activity.
- 3
Cristae
Membranes protected and swelling prevented after ischemia.
- 4
ATP
Recovered quickly on reperfusion.
Surface electrostatics
A 2020 study in the Journal of Biological Chemistry used biophysical and computational methods to look at how SS-31 interacts with lipid bilayers. The peptide carries several positive charges, and it settled into the membrane interface at a level that tracked surface charge. It didn't destabilize the bilayer. It did change lipid packing and the membrane's surface electrostatics. The authors proposed that this tuning of surface charge could explain the protective effects. They also showed that SS-31 shifted calcium distribution at the interface and lowered the energetic cost of calcium stress in mitochondria.
Clinical program
A 2025 review in the International Journal of Molecular Sciences lists clinical studies of elamipretide, among them PROGRESS-HF, TAZPOWER, MMPOWER-3 and ReCLAIM, plus preclinical work in models of heart failure, neurodegeneration, ischemia-reperfusion injury, metabolic syndromes and muscle weakness. Its conclusion is that long-term efficacy and safety still need study. MMPOWER-3, a randomized trial in primary mitochondrial myopathy, was published in Neurology in 2023.
An unsettled mechanism
Most of the mechanistic data comes from cells, isolated mitochondria and animals, and the mechanism is still debated. The two papers above show how: one stresses direct interaction with cardiolipin and cytochrome c, the other stresses changes in membrane electrostatics. Anyone trying to reproduce this work needs a certificate of analysis showing identity and purity for the specific batch.
References
- Birk AV et al. The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin. J Am Soc Nephrol 2013.
- Mitchell W et al. The mitochondria-targeted peptide SS-31 binds lipid bilayers and modulates surface electrostatics as a key component of its mechanism of action. J Biol Chem 2020.
- Tung C et al. Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential. Int J Mol Sci 2025.
- Karaa A et al. Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial. Neurology 2023.