Recombinant TGF-beta 1 is synthesized as a two-component latent complex that shares some structural features with the native platelet latent TGF-beta 1 complex.
The entire coding region of the human transforming growth factor beta 1 (TGF-beta 1) precursor cDNA has been stably expressed in a human renal carcinoma cell line. Like platelet TGF-beta 1, the recombinant TGF-beta 1 is secreted in a biologically latent form. Immunoblot analysis and gel-filtration indicate that the recombinant latent TGF-beta 1 is a 100-kDa complex in which active 25-kDa TGF-beta 1 is noncovalently associated with the remaining 75 kDa of the processed precursor. Unlike the platelet latent complex, the recombinant latent complex contains no 135-kDa component. Thus, the processed precursor peptide alone is sufficient to confer latency on active TGF-beta 1, and the 135-kDa platelet component has a different role. The processed precursor is similarly glycosylated in recombinant and platelet complexes, and in both has an exposed heparin binding site that may be involved in targeting of the latent complex. Finally, acid activation of recombinant and platelet complexes is reversible, suggesting that the activation process does not cause major structural modifications in the components of the latent complex.
Wakefield
L M
LM
Laboratory of Chemoprevention, National Cancer Institute, Bethesda, MD 20892.
Smith
D M
DM
Broz
S
S
Jackson
M
M
Levinson
A D
AD
Sporn
M B
MB
D001665:Binding Sites / Q000502:physiology; D001792:Blood Platelets / Q000378:metabolism*; D002460:Cell Line; D002853:Chromatography, Liquid; D002872:Chromosome Deletion; D006031:Glycosylation; D006493:Heparin / Q000378:metabolism; D006801:Humans; D006851:Hydrochloric Acid; D015151:Immunoblotting; D008970:Molecular Weight; D010957:Plasmids / Q000235:genetics; D011498:Protein Precursors / Q000097:blood; D011863:Radioimmunoassay; D011869:Radioligand Assay; D011994:Recombinant Proteins / Q000096:biosynthesis; D014162:Transfection; D015291:Transforming Growth Factors / Q000096:biosynthesis* / Q000097:blood / Q000502:physiology
D011498:Protein Precursors; D011994:Recombinant Proteins; D015291:Transforming Growth Factors; D006493:Heparin; D006851:Hydrochloric Acid