Amino acids 67 and 68 of transforming growth factor-beta regulate binding to a glycosyl phosphatidyl inositol-linked membrane protein on vascular endothelial cells.
Transforming growth factor-beta (TGF-beta) is a multifunctional growth and differentiation factor that affects almost all cells. Although equipotent in many cases, the three isoforms of TGF-beta (-beta1, -beta2, -beta3) have several important isoform specific activities. For example, TGF-beta2 binds with higher affinity to a 60 kDa cell-surface glycosyl phosphatidylinositol (GPI)-linked protein, expressed on vascular endothelial cells. We used chimeric TGF-beta proteins, in which selected regions of TGF-beta1 had been exchanged for the corresponding region of TGF-beta2, to demonstrate that amino acids 67 and 68 regulate binding of TGF-beta to this protein. Exchange of amino acids 67 and 68 of TGF-beta1 into TGF-beta2 resulted in a protein similar in affinity to TGF-beta1 for binding to the GPI-linked protein. In contrast, exchange of only amino acid 67 of TGF-beta1 into TGF-beta2, or exchange of only amino acid 68 of TGF-beta1 into TGF-beta2, resulted in a protein with affinity similar to that of TGF-beta2. This suggests that the coordinated change of Gln and His of TGF-beta1 to Thr and Ile at positions 67 and 68 alters the specificity of TGF-beta. Amino acids 67 and 68 are part of a surface-exposed alpha-helix that forms a projection away from the center of the TGF-beta molecule and is accessible for receptor binding.
Zhang
K Q
KQ
Marshfield Medical Research Foundation, WI 54449, USA.
Polga
D
D
Salzman
S A
SA
Burmester
J K
JK
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003545:Cysteine / Q000737:chemistry; D004730:Endothelium, Vascular / Q000166:cytology* / Q000378:metabolism; D007532:Isoleucine / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013552:Swine; D013912:Threonine / Q000737:chemistry; D016212:Transforming Growth Factor beta / Q000737:chemistry* / Q000378:metabolism; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2
D003432:Cross-Linking Reagents; D008024:Ligands; D011993:Recombinant Fusion Proteins; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2; D007532:Isoleucine; D013912:Threonine; D003545:Cysteine