TB-500

TB-500 is a synthetic analogue of the 43 amino acid Thymosin Beta-4 (Tb4) peptide, reproducing the complete native sequence with greater than or equal to 98% HPLC-verified purity. Thymosin Beta-4 is the most abundant member of the beta-thymosin family — small acidic intracellular proteins that function as G-actin sequestering agents regulating actin monomer availability for cytoskeletal dynamics. Tb4 is encoded by the TMSB4X gene and expressed at high levels in platelets, macrophages, neutrophils, and most other cell types, making it one of the most abundant proteins in mammalian cells (approximately 0.5% of total soluble protein).

The primary molecular mechanism of TB-500 is direct G-actin (globular actin monomer) sequestration through its LKKTET hexapeptide motif at positions 17-22. Structural studies using X-ray crystallography and NMR have established that the LKKTET sequence binds to the barbed face of the G-actin monomer, occupying a cleft that overlaps with the D-loop region normally involved in actin-actin contacts within F-actin filaments. By binding this barbed-face site, TB-500 prevents G-actin incorporation into growing F-actin filament barbed ends, maintaining a larger pool of sequestered G-actin monomers available for rapid filament assembly when protrusion signals are received.

The G/F-actin equilibrium regulated by TB-500 is central to lamellipodia formation and directed cell migration. Lamellipodia — the flat actin-rich protrusions at the leading edge of migrating cells — require rapid actin polymerisation from the Arp2/3-nucleated branched network. The rate of actin branching is limited by G-actin monomer availability: TB-500 modulates this availability by controlling the size of the sequestered pool. In wound healing scratch assays and transwell migration assays, TB-500 treatment increases migration speed and persistence of directionality through this actin dynamics mechanism.

TB-500's second biological mechanism involves integrin-linked kinase (ILK) activation — a function distinct from the LKKTET actin-sequestering activity. Bock-Marquette et al. (Nature, 2004) published that Thymosin Beta-4 directly binds and activates ILK, promoting Akt phosphorylation at Ser473 (survival signalling) and driving cell migration through ILK-dependent PI3K pathway activation. This ILK mechanism is independent of actin binding and occurs at focal adhesion complexes where ILK connects integrin cytoplasmic tails to the cytoskeleton through PINCH-parvin interactions.

Cardiac research: Smart et al. (Nature, 2007) published that Thymosin Beta-4 administration mobilised quiescent epicardial progenitor cells (EPDCs) and promoted their migration into ischaemic myocardium, where they differentiated into smooth muscle cells and contributed to neovascularisation. This landmark study positioned Thymosin Beta-4 as a cardiac tissue regeneration research tool and generated extensive subsequent research into epicardial progenitor biology.

Corneal epithelial research connects TB-500 to one of the highest-expressing tissues for Thymosin Beta-4 in the body — the corneal epithelium. High Tb4 expression supports rapid corneal wound healing, and published research has examined TB-500 in corneal re-epithelialisation models following alkali injury and in dry eye disease models.

Research endpoints: G/F-actin ratio (Triton X-100 solubility fractionation, Western blot of supernatant and pellet fractions); lamellipodia quantification by phalloidin staining and confocal imaging; scratch assay migration rate; transwell migration (directed migration); ILK kinase activity assay; phospho-Akt (Ser473) Western blot; and Matrigel tube formation for angiogenesis.

MW: 4963.5 g/mol. CAS: 77591-33-4. Reconstitute in bacteriostatic water at 1mg/mL. Store lyophilised at -20°C. For laboratory and analytical research purposes only.