Actin Regulation & Cell Migration Pathways
Thymosin Beta-4 Synthetic Fragment (Ac-LKKTETQ)
TB-500 (also referenced in research literature as TB500, tb-500 peptide, or Thymosin Beta-4 fragment) is a synthetic heptapeptide corresponding to the N-acetylated active fragment (amino acids 17–23) of thymosin beta-4 (Tβ4), a naturally occurring 43-amino-acid protein found ubiquitously in human and animal tissues. Thymosin beta-4 was first isolated from thymic tissue in the 1960s and has since been recognized as a master regulator of actin dynamics — the cytoskeletal processes that govern cell shape, movement, and division.
The TB-500 fragment (Ac-LKKTETQ) retains the actin-binding domain of the full-length thymosin beta-4 molecule, which is responsible for the peptide's primary biological activities in preclinical research models.
TB-500 consists of seven amino acids: Leucine-Lysine-Lysine-Threonine-Glutamate-Threonine-Glutamine, with an N-terminal acetyl group (Ac-LKKTETQ). This acetylation is functionally significant — it protects the peptide from aminopeptidase degradation and is required for full actin-sequestering activity.
The compound has a molecular weight of approximately 887.0 Daltons. Despite its reduced size compared to the full thymosin beta-4 molecule, TB-500 retains the critical WH2 (Wiskott-Homology 2) actin-binding motif, which is the structural basis for its primary mechanism of action.
The central mechanism of TB-500 revolves around its capacity to bind monomeric G-actin (globular actin) and thereby regulate the equilibrium between G-actin and filamentous F-actin. Actin dynamics are essential for virtually every aspect of cell motility, including the directed migration of repair cells to sites of tissue injury.
By sequestering G-actin, TB-500 reduces the pool available for F-actin polymerization in a spatially controlled manner, effectively enabling cells to extend lamellipodia and migrate toward chemotactic gradients. This mechanism is particularly relevant to wound healing, where fibroblasts, endothelial cells, and keratinocytes must migrate into the wound bed to initiate repair.
Beyond actin regulation, preclinical research has identified additional activities of TB-500, including promotion of endothelial cell differentiation and angiogenesis, inhibition of inflammatory cytokine expression (notably IL-1β and TNF-α), and activation of the Akt survival signaling pathway, which confers cytoprotective effects in ischemic tissue models.
TB-500 is a synthetic version of a small fragment of a protein your body already produces naturally, called Thymosin Beta-4. This protein is found in virtually every cell in your body and plays a key role in how cells move and organize themselves during repair.
TB-500's main job in research models is enabling cells to move. Specifically, it interacts with actin — the internal scaffolding protein that gives cells their shape and allows them to crawl. By regulating actin dynamics, TB-500 appears to help repair cells migrate from where they're stored to where they're needed. Imagine a city after a storm: TB-500 is studied for its potential role in clearing the roads so repair crews can actually reach the damage.
Many tissues fail to heal properly not because the body lacks repair cells, but because those cells can't efficiently navigate to the injury site. TB-500's actin-regulating mechanism is particularly interesting to researchers because it works systemically — meaning it may influence cell movement throughout the body, not just at a specific local site. This distinguishes it from more locally-acting compounds like BPC-157.
TB-500 has a stronger clinical research foundation than most peptides in this category — its parent molecule (full-length Thymosin Beta-4) has been studied in human trials for wound healing and dry eye. TB-500 itself is a shorter, more targeted fragment. All current TB-500 research is preclinical; it is a research compound only.
Binds monomeric G-actin via the WH2 domain, regulating cytoskeletal dynamics and enabling directed cell migration.
Activates the Akt pathway, promoting cellular survival and providing cytoprotection in ischemic and inflammatory conditions.
Promotes endothelial cell differentiation and new vessel formation through mechanisms partially independent of classical VEGF signaling.
Downregulates pro-inflammatory cytokines including IL-1β and TNF-α, reducing inflammatory burden at sites of tissue injury.
3 cited studies — model, sample size, outcome, and effect size from published literature.
| Study | Model | Sample | Outcome | Effect Size | Level |
|---|---|---|---|---|---|
Goldstein AL, et al. (2012) Thymosin β4: a multi-functional regenerative peptide PubMed | Rodent + human cardiac (Phase II) | Phase II: n=44 | Improved cardiac function post-MI; reduced fibrosis; stem cell mobilization | Significant improvement in ejection fraction vs. placebo (Phase II) | Phase II |
Huff T, et al. (2001) Thymosin β4 is released from human blood platelets and attached to actin filamen… PubMed | Human platelet — in vitro | In vitro | Confirmed Tβ4 sequestration of G-actin; mechanism of actin polymerization modulation | Quantitative G-actin binding demonstrated | In Vitro |
Sosne G, et al. (2010) Thymosin beta 4 and the eye: I can see clearly now the pain is gone PubMed | Human — Phase II (corneal injury) | n=72 | Significant improvement in corneal wound healing and pain reduction | Faster re-epithelialization vs. vehicle (p<0.01) | Phase II |
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| Peptide Class | Synthetic heptapeptide (7 amino acids) |
| Molecular Weight | 887.0 Da |
| Amino Acid Sequence | Ac-LKKTETQ |
| Parent Molecule | Thymosin beta-4 (residues 17–23) |
| Key Structural Feature | N-terminal acetylation; WH2 actin-binding domain |
| Available Sizes | 10mg vials |
| Form | Lyophilized peptide powder |
| Purity | ≥99% (third-party tested) |
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Purchase TB-500 at Purgo LabsMedical Disclaimer: All content on this site is for educational and research purposes only. Research peptides are not FDA-approved for human use. Always consult a qualified healthcare professional before considering any peptide or supplement protocol. Nothing on this site constitutes medical advice, diagnosis, or treatment.
