Identification of a structural domain that distinguishes the actions of the type 1 and 2 isoforms of transforming growth factor beta on endothelial cells.

A chimeric transforming growth factor beta (TGF-beta) molecule has been synthesized to map the amino acids responsible for the substantially greater activity of TGF-beta 1 than TGF-beta 2 on growth and migration of endothelial cells. This chimera consists of a dimer of a monomeric unit composed of amino acids 1-39 of TGF-beta 2, 40-82 of TGF-beta 1, and 83-112 of TGF-beta 2. Structural identity of the purified recombinant protein has been confirmed by immunoblotting and NH2-terminal sequencing. The biological potency of the TGF-beta 2-1-2 chimera was equal to that of TGF-beta 1 in inhibition of growth of both fetal bovine heart endothelial cells and rat epididymal fat pad microvascular endothelial cells. Similarly, the TGF-beta 2-1-2 chimera was nearly equivalent to TGF-beta 1 and at least 10-fold more active than TGF-beta 2 in inhibiting migration of bovine aortic endothelial cells. These results identify the sequence between amino acids 40-82 as an important region within TGF-beta that functions to specify a TGF-beta 1- or TGF-beta 2-like activity. IMAGES: