A 16-amino acid peptide from human alpha2-macroglobulin binds transforming growth factor-beta and platelet-derived growth factor-BB.
Alpha2-macroglobulin (alpha2M) is a major carrier of transforming growth factor-beta (TGF-beta) in vitro and in vivo. By screening glutathione S-transferase (GST) fusion proteins with overlapping sequences, we localized the TGFbeta-binding site to aa 700-738 of the mature human alpha2M subunit. In separate experiments, we screened overlapping synthetic peptides corresponding to aa 696-777 of alpha2M and identified a single 16-mer (718-733) that binds TGF-beta1. Platelet-derived growth factor-BB (PDGF-BB) bound to the same peptide, even though TGF-beta and PDGF-BB share almost no sequence identity. The sequence of the growth factor-binding peptide, WDLVVVNSAGVAEVGV, included a high proportion of hydrophobic amino acids. The analogous peptide from murinoglobulin, a human alpha2M homologue that does not bind growth factors, contained only three nonconservative amino acid substitutions; however, the MUG peptide failed to bind TGF-beta1 and PDGF-BB. These results demonstrate that a distinct and highly-restricted site in alpha2M, positioned near the C-terminal flank of the bait region, mediates growth factor binding. At least part of the growth factor-binding site is encoded by exon 18 of the alpha2M gene, which is notable for a 5' splice site polymorphism that has been implicated in Alzheimer's Disease.
Webb
D J
DJ
Department of Pathology, University of Virginia School of Medicine, Charlottesville 22908, USA.
Roadcap
D W
DW
Dhakephalkar
A
A
Gonias
S L
SL
D000595:Amino Acid Sequence; D000077214:Becaplermin; D001665:Binding Sites; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000737:chemistry / Q000378:metabolism*; D021122:Protein Subunits; D020574:Proto-Oncogene Proteins c-sis; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D016212:Transforming Growth Factor beta / Q000737:chemistry / Q000378:metabolism*; D000511:alpha-Macroglobulins / Q000737:chemistry* / Q000378:metabolism*
D010446:Peptide Fragments; D010455:Peptides; D010982:Platelet-Derived Growth Factor; D021122:Protein Subunits; D020574:Proto-Oncogene Proteins c-sis; D011993:Recombinant Fusion Proteins; D016212:Transforming Growth Factor beta; D000511:alpha-Macroglobulins; D000077214:Becaplermin