Binding affinity of transforming growth factor-beta for its type II receptor is determined by the C-terminal region of the molecule.
Transforming growth factor-beta (TGF-beta) isoforms have differential binding affinities for the TGF-beta type II receptor (TbetaRII). In most cells, TGF-beta1 and TGF-beta3 bind to TbetaRII with much higher affinity than TGF-beta2. Here, we report an analysis of the effect of TGF-beta structure on its binding to TbetaRII by using TGF-beta mutants with domain deletions, amino acid replacements, and isoform chimeras. Examination of the binding of TGF-beta mutants to the recombinant extracellular domain of TbetaRII by a solid-phase TGF-beta/TbetaRII assay demonstrated that only those TGF-beta mutants containing the C terminus of TGF-beta1 (TGF-beta1-(Delta69-73), TGF-beta1-(Trp71), and TGF-beta2/beta1-(83-112)) bind with high affinity to TbetaRII, similar to native TGF-beta1. Moreover, replacement of only 6 amino acids in the C terminus of TGF-beta1 with the corresponding sequence of TGF-beta2 (TGF-beta1/beta2-(91-96)) completely eliminated the high affinity binding of TGF-beta1. Proliferation of fetal bovine heart endothelial (FBHE) cells was inhibited to a similar degree by all of the TGF-beta mutants. However, recombinant soluble TbetaRII blocked the inhibition of FBHE cell proliferation induced by TGF-beta mutants retaining the C terminus of TGF-beta1, consistent with the high binding affinity between these TGF-beta molecules and TbetaRII. It was further confirmed that the TGF-beta2 mutant with its C terminus replaced by that of TGF-beta1 (TGF-beta2/beta1-(83-112)) competed as effectively as TGF-beta1 with 125I-TGF-beta1 for binding to membrane TbetaRI and TbetaRII on FBHE cells. These observations clearly indicate that the domain in TGF-beta1 responsible for its high affinity binding to TbetaRII, both the soluble and membrane-bound forms, is located at C terminus of the molecule.
Qian
S W
SW
Laboratory of Chemoprevention, NCI, National Institutes of Health, Bethesda, Maryland 20892-5055, USA.
Burmester
J K
JK
Tsang
M L
ML
Weatherbee
J A
JA
Hinck
A P
AP
Ohlsen
D J
DJ
Sporn
M B
MB
Roberts
A B
AB
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D001681:Biological Assay; D002417:Cattle; D002455:Cell Division; D002478:Cells, Cultured; D018604:Epitope Mapping; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins; D016415:Sequence Alignment; D012995:Solubility; D013329:Structure-Activity Relationship; D016212:Transforming Growth Factor beta / Q000737:chemistry* / Q000378:metabolism
D018125:Receptors, Transforming Growth Factor beta; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II