A central domain binding site in insulin-like growth factor binding protein-5 for the acid-labile subunit.
Like insulin-like growth factor binding protein-3 (IGFBP-3), IGFBP-5 forms a ternary complex with insulin-like growth factor (IGF)-I or IGF-II, and the acid-labile subunit (ALS). The study of IGFBP-5/IGFBP-6 chimeric proteins with amino-terminal and middle domain swaps, has revealed the existence of a site in the middle domain of IGFBP-5, that binds to ALS in the absence of the IGFBP-5 carboxy-terminal domain. An IGFBP-6 chimeric protein containing the central domain of IGFBP-5 complexed efficiently with ALS, and a carboxy-terminally truncated IGFBP-5 mutant, IGFBP-5'(1-169), also bound to ALS in the presence of IGFs, although with much less potency than full length rhIGFBP-5. In contrast to the latter, IGFBP-5(1-169) preferentially formed ternary complexes with IGF-II rather than IGF-I. These results indicate that a site which binds ALS exists in IGFBP-5 mutants which lack the IGFBP-5 carboxy-terminal domain.
Twigg
S M
SM
Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, St Leonards, NSW, Australia.
Kiefer
M C
MC
Zapf
J
J
Baxter
R C
RC
D001665:Binding Sites; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000737:chemistry* / Q000235:genetics; D018976:Insulin-Like Growth Factor Binding Protein 6 / Q000737:chemistry / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000737:chemistry; D007335:Insulin-Like Growth Factor II / Q000737:chemistry; D011233:Precipitin Tests; D011994:Recombinant Proteins / Q000737:chemistry; D016622:Silver Staining; D013002:Somatomedins / Q000737:chemistry* / Q000235:genetics
D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D006023:Glycoproteins; D018975:Insulin-Like Growth Factor Binding Protein 5; D018976:Insulin-Like Growth Factor Binding Protein 6; D011994:Recombinant Proteins; D013002:Somatomedins; C075944:insulin-like growth factor binding protein, acid labile subunit; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II