What is Thymosin Beta-4?
Thymosin Beta-4 (Tβ4) is a naturally occurring polypeptide consisting of 43 amino acids found in nearly all tissues and cells of the human organism. It was first isolated from bovine thymus in 1966 and is one of the most abundant intracellular peptides, with concentrations of up to 0.5 mM in blood platelets.
The primary biochemical function of Tβ4 is the sequestration of G-actin (monomeric actin) — it binds G-actin with high affinity, thereby regulating the balance between G-actin and F-actin (filamentous actin) within the cell.
What is TB-500?
TB-500 (Ac-LKKTETQ-NH₂) is a synthetic heptapeptide corresponding to the G-actin-binding domain of Thymosin Beta-4 — amino acid residues 17 to 23 of the Tβ4 sequence. It is N-terminally acetylated and C-terminally amidated.
| Parameter |
TB-500 |
Thymosin Beta-4 |
| Amino acids |
7 |
43 |
| Sequence |
Ac-LKKTETQ-NH₂ |
43 AA complete sequence |
| Molecular weight |
877.99 g/mol |
4963 g/mol |
| CAS |
885340-08-9 |
61512-21-8 |
| Origin |
Synthetic · Tβ4 Res. 17–23 |
Natural · Bovine thymus |
Important
TB-500 is not identical to Thymosin Beta-4. It is the isolated active fragment of the G-actin-binding domain. The biochemical properties of the two compounds overlap but are not congruent.
G-actin-binding domain
The sequence LKKTETQ corresponds to the central motif of the G-actin-binding domain in Thymosin Beta-4. This region is responsible for the interaction with G-actin — the peptide binds to the actin subunit and prevents its polymerization into F-actin.
In cell culture systems, TB-500 modulates actin dynamics, thereby influencing cellular processes dependent on cytoskeletal organization — including cell migration, cell adhesion, and intracellular transport.
Documented research areas
- →G-actin sequestration — actin polymerization kinetics in cell extracts
- →VEGFR2 signal transduction — angiogenesis signaling pathways in HUVEC cultures
- →Cell migration assays — scratch assays in endothelial cell cultures
- →Cytoskeletal imaging — fluorescence microscopy of actin filament dynamics