Requirement for Activin a and Transforming Growth Factor--β1 Pro-Regions in Homodimer Assembly

Many proteins are initially synthesized as part of a large precursor. The role of the pro-region in the biosynthesis of transforming growth factor--beta 1 (TGF-beta 1) and activin A, two structurally related disulfide-linked homodimers synthesized as large precursors, was studied. Vectors that expressed either the pro-region or the mature regions of these molecules were used in complementation experiments, only when the pro-region was coexpressed with the mature region did intracellular dimerization and secretion of biologically active homodimers occur. The pro-regions of activin A and TGF-beta 1, therefore, aid the folding, disulfide bond formation, and export of their respective homodimers.