What Is SS-31 Peptide?
SS-31 is a synthetic tetrapeptide in the Szeto-Schiller peptide family. It is also known as elamipretide. The peptide consists of D-arginine, 2,6-dimethyltyrosine, lysine and phenylalanine residues, giving it a distinctive aromatic-cationic structure.
SS-31 is classified as a mitochondria-targeted peptide because of its characteristic molecular structure and mitochondrial localization described in published research. It has been studied extensively as a distinct member of the Szeto-Schiller peptide class.
Research Overview Table
Chemical and Molecular Characteristics
SS-31 (elamipretide) is a synthetic tetrapeptide in the Szeto-Schiller peptide class. Its structure contains D-arginine, 2,6-dimethyl-L-tyrosine, L-lysine, and L-phenylalaninamide residues. The combination of charged and aromatic amino acid residues gives SS-31 a distinctive molecular architecture.
The presence of a D-amino acid and a modified tyrosine residue distinguishes SS-31 from many conventional peptides composed solely of standard L-amino acids. These structural features are important when describing the compound's chemical identity and classification within mitochondria targeted peptide research.
Certificates:
Mechanism of Action Under Investigation
SS-31 interacts selectively with cardiolipin in the inner mitochondrial membrane through electrostatic and hydrophobic interactions. Experimental studies show that SS-31 binds cardiolipin containing membranes and changes their surface electrostatics without destabilizing the lipid bilayer.
The SS-31–cardiolipin interaction also modifies the cardiolipin–cytochrome c complex. Studies found reduced cytochrome c peroxidase activity while preserving its electron transfer function. Other experiments reported effects on mitochondrial respiration and ATP synthesis. Protein-interaction studies have identified additional cardiolipin associated mitochondrial proteins, but their contribution to SS-31's overall mechanism remains uncertain.
Scientific Research Context
Researchers have studied SS-31 in several areas of mitochondrial research. The literature includes biochemical work, cell experiments, isolated mitochondria, and animal studies. Most of the evidence comes from in vitro research and preclinical animal work. Human studies make up a smaller part of the literature, so the overall research base remains predominantly preclinical.
SS-31 Biology and Biological Pathways
Primary Biological Function
Mitochondria regulate cellular energy production, metabolite processing, calcium handling, and cell signaling. Cardiolipin is a specialized phospholipid of the inner mitochondrial membrane. It supports membrane organization and the activity of several mitochondrial protein complexes. These functions make mitochondrial membrane biology an important area of SS-31 research.
Relevant Metabolic or Signaling Pathways
SS-31 research has examined mitochondrial oxidative phosphorylation and 2-oxoglutarate metabolism. Protein-interaction studies identified SS-31-associated mitochondrial proteins involved in ATP production and 2-oxoglutarate metabolic processes. These pathways are therefore relevant to research on mitochondrial energy metabolism.
Tissue-Specific Biology
Mitochondrial biology differs among tissues because energy requirements and metabolic activity are not uniform. SS-31 research has therefore examined tissues including skeletal muscle, cardiac tissue, kidney, nervous tissue and retinal tissue. These studies provide different biological settings for examining mitochondrial structure and function.
Experimental Biomarkers
SS-31 studies have measured mitochondrial oxygen consumption, ATP production, respiratory-chain activity, membrane potential, cardiolipin composition and reactive oxygen species. Researchers also assess mitochondrial structure and protein activity to characterize changes in mitochondrial function.
Laboratory Investigation Methods
Researchers have used respirometry to measure mitochondrial oxygen consumption and fluorescence spectroscopy to examine SS-31–cardiolipin interactions. Nuclear magnetic resonance has also been used to study molecular interactions. while chemical cross-linking with LC-MS has identified SS-31-associated mitochondrial proteins.
Experimental Models Used in Published Research
Published SS-31 studies use several experimental systems, ranging from simplified membrane preparations to isolated mitochondria, cultured cells and animal models. These systems differ in complexity and physiological context, so each has limitations when used to represent mitochondrial biology in intact organisms.
Model Lipid Membranes
Model lipid membranes are used to study SS-31 under controlled membrane conditions. Their limitation is their simplified composition. They cannot reproduce the full range of proteins, lipids and cellular interactions present in an intact mitochondrial membrane.
Isolated Mitochondria
Isolated mitochondria allow researchers to examine mitochondrial processes outside intact cells. The main limitation is removal from the surrounding cellular environment. Tissue source and mitochondrial isolation procedures can also influence the characteristics of the preparation.
Cultured Cells
Cultured cells provide an intact cellular setting for SS-31 research under controlled laboratory conditions. Their limitations include artificial culture conditions and the absence of normal tissue architecture, systemic regulation, and interactions between different organs.
Yeast Mitochondria
Saccharomyces cerevisiae mitochondria have been used to examine SS-31 in systems with defined cardiolipin metabolism. The model permits comparison of different cardiolipin states. Its limitation is that yeast mitochondrial biology differs from that of mammalian cells.
Mouse Models
Mouse models allow SS-31 to be studied within an intact mammalian system. Published research includes aging, neurological, cardiac, skeletal muscle and other experimental models. Their main limitation is species-specific physiology, which limits direct translation to human biology.
Rat Models
Rat models have been used in several areas of SS-31 research, including renal, neurological, and cardiac investigations. They provide whole-organism physiology but remain limited by species differences in metabolism, mitochondrial biology and tissue responses compared with humans.
Published Scientific Research
Mitochondrial Bioenergetics
Published SS-31 research has investigated mitochondrial respiration, oxidative phosphorylation, ATP production and ADP sensitivity. Studies have also examined mitochondrial energetic capacity in aged skeletal muscle and older adults. The research therefore focuses on how SS-31 relates to mitochondrial energy production and the regulation of ADP-driven respiration.
Cardiolipin and Mitochondrial Membranes
Another major area of investigation concerns SS-31 and cardiolipin within mitochondrial membranes. Studies have examined how SS-31 interacts with cardiolipin and how this relationship relates to membrane organization and mitochondrial function. Research has included model membranes and mitochondrial preparations.
Mitochondrial Protein Interactions
Researchers have investigated whether SS-31 associates with mitochondrial proteins in addition to its lipid interactions. Published work identified proteins associated with oxidative phosphorylation, ADP/ATP transport, ATP synthesis and 2-oxoglutarate metabolism. This research broadened investigation of the molecular components associated with SS-31.
Aging and Skeletal Muscle
Age-related skeletal muscle research has examined SS-31 in connection with mitochondrial ATP production, oxidative phosphorylation coupling, ADP sensitivity and skeletal muscle bioenergetics. Studies have addressed these questions in aged mice, isolated muscle mitochondria, and older adults. Human research has also examined mitochondrial energetic capacity in aging skeletal muscle.
Cardiac Mitochondrial Biology
Cardiac research has investigated SS-31 in relation to mitochondrial respiration, cardiac bioenergetics, mitochondrial dynamics, membrane organization and cardiolipin biology. Studies have also examined age-related cardiac mitochondrial changes and mitochondrial abnormalities associated with Barth syndrome. Published work includes human cardiac tissue and animal research.
Mitochondrial Disorders
SS-31 research in mitochondrial disorders has focused particularly on Barth syndrome and DCMA, two disorders involving mitochondrial abnormalities. Published studies have examined cardiolipin-related mitochondrial changes, mitochondrial structure, bioenergetics and muscle and cardiac biology in these conditions. Clinical research has also investigated elamipretide in people with Barth syndrome.
Limitations of Current Research
Evidence Is Predominantly Preclinical
SS-31 has been studied extensively in cellular, mitochondrial and animal research. Human studies are also available, but they cover a narrower range of research questions and populations. The overall literature therefore remains weighted toward preclinical evidence rather than large, controlled clinical studies.
Human Clinical Evidence
Human evidence is limited by the number and size of clinical studies. For example, the randomized TAZPOWER study enrolled 12 participants with Barth syndrome, while a randomized study in older adults included 39 participants. These populations also represent specific research groups rather than a broad human population.
Species Differences
Animal studies of SS-31 include different rodent species and disease models, while human studies provide a separate biological context. Differences in mitochondrial physiology, metabolism and tissue responses between species can affect how closely animal findings reflect human biology. These differences limit direct extrapolation from experimental animals to humans.
Study Design Limitations
SS-31 studies use different designs, including randomized placebo-controlled trials, crossover studies, open-label extensions, and retrospective comparisons. The Barth syndrome trial, for example, used a randomized crossover design followed by an open-label extension, while a separate study used a retrospective natural-history comparison. These design differences limit direct comparison across studies.
Independent Replication
The extent of independent replication differs across SS-31 research areas. Some biological questions have been examined in several experimental systems whereas other findings come from more limited sets of studies. This uneven replication means that the strength of confirmation is not the same across the entire SS-31 literature.
Long-Term Evidence
Longer-term human data are available, but they come mainly from specific clinical populations. The TAZPOWER open-label extension followed participants for up to 168 weeks, with 8 participants reaching the final assessment. This provides longer-duration evidence in Barth syndrome but comparable long-term data remain limited in other populations.
Analytical Documentation
HPLC can be used to assess peptide purity and separate related substances. LC-MS provides mass-based information that can support peptide identity and characterization. Published SS-31 research has used liquid chromatography with mass spectrometry for peptide and protein analysis.
NMR has also been used in structural research involving SS-31 and related tetrapeptides, including studies of their membrane-bound structure.
A Certificate of Analysis (CoA) records batch-specific testing and reported specifications. Together, these records provide complementary information about the chemical identity and quality of laboratory material. Analytical documentation verifies product identity and quality rather than biological performance.
Storage and Laboratory Handling
SS-31 should be handled by qualified laboratory personnel using appropriate laboratory procedures and clean equipment. Keep the container closed when not in use to help prevent contamination.
Store SS-31 at 2–8°C according to the specified product conditions. Keep the material in appropriate storage conditions and avoid unnecessary temperature changes. SS-31 is intended for laboratory research use only.
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