Mouse TGF beta 1 Carrier-Free Recombinant Protein, eBioscience?. TGF beta-1 (TGFB1, Transforming Growth Factor Beta 1) is a polypeptide member of the transforming growth factor beta superfamily of cytokines, found almost ubiquitously in tissues. Transforming growth factor (TGF)-b is stored in the extracellular matrix as a latent complex with its pro-domain. Activation of TGF beta-1 requires the binding of aV integrin to an RGD sequence in the prodomain and exertion of force on this domain, which is held in the extracellular matrix by latent TGF-b binding proteins. Latent forms are complexes of TGF beta-1, an amino-terminal portion of the TGF-beta precursor, designated TGF-LAP (TGF-latency associated peptide), and a specific binding pr