Transforming growth factor beta 1 (TGF-β1) is a member of the transforming growth factor beta superfamily of cytokines. TGF-β1 precursor contains a pro-region (latency associated peptide or LAP), and C-terminal region that becomes active TGF-β1 upon activation. Both LAP and TGF- β1 exist as homodimers in circulation, but the disulfide-linked homodimers of LAP and TGF-β1 remain non-covalently associated, forming the small latent TGFβ1 complex. The large latent TGF- β1 Complex contains a third component, the latent TGF-β binding protein (LTBP), which is linked to LAP by a single disulfide bond. LTBP does not confer latency, but is required for efficient secretion of the complex to extracellular sites. Free active TGF-β1 can be released by many factors, including enzymes and low or high pH. It has diverse biological functions in multiple cellular processes, with its intracellular signaling pathways being associated with regulation of proliferation and differentiation to various cell types.
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