The pro domain of pre-pro-transforming growth factor beta 1 when independently expressed is a functional binding protein for the mature growth factor.
Transforming growth factor beta 1 (TGF-beta 1) is proteolytically derived from the carboxyl terminus of a 390 amino acid precursor molecule termed pre-pro-TGF-beta 1. Previous studies have suggested that the pro piece of pre-pro-TGF-beta 1 may play an important role in the formation of an inactive, latent complex. These latent forms are thought to be important in the regulation of TGF-beta 1 activity. To understand this latent complex in more detail, we have expressed the pro domain of pre-pro-TGF-beta 1 in tissue culture cells independent of the mature growth factor. A stop codon was genetically engineered into the cDNA of pre-pro-TGF-beta 1 by changing the Arg-278 codon from CGA to the STOP codon TGA. The resulting protein is truncated just prior to the amino-terminal Ala residue of the mature growth factor. Transient expression studies and immunoblotting indicate that this pro piece is readily made and secreted by the COS-1 cells; the major form of the expressed pro piece, when analyzed by SDS-polyacrylamide gel electrophoresis, behaves as a disulfide-linked dimer (Mr 80,000). Bioassays, using mink lung indicator cells, reveal that the pro domain forms an inactive complex with exogenously added mature TGF-beta 1. Treatment of this complex with heat or acid results in the release of active TGF-beta 1, indicating an in vitro structure similar to natural, latent TGF-beta 1 complexes. The pro piece from TGF-beta 1 was also found to form latent structures with two closely related family members, TGF-beta 1.2 and TGF-beta 2.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Biochemistry, Medical College of Ohio, Toledo 43699.
L E
LE
Gentry
B W
BW
Nash
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics; D004247:DNA / Q000235:genetics; D015870:Gene Expression; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D011498:Protein Precursors / Q000235:genetics; D011506:Proteins / Q000235:genetics; D016212:Transforming Growth Factor beta; D015291:Transforming Growth Factors / Q000235:genetics
D002352:Carrier Proteins; D011498:Protein Precursors; D011506:Proteins; D016212:Transforming Growth Factor beta; D015291:Transforming Growth Factors; D004247:DNA