Cloning, sequence analysis and expression of a cDNA encoding a novel insulin-like growth factor binding protein (IGFBP-2).
Insulin-like growth factors bind with high affinity to specific binding proteins in extracellular fluids. To identify structural characteristics of IGF-binding proteins that might define their physiological roles, we determined the complete primary structure of a novel human IGF-binding protein (IGFBP-2) from a cloned cDNA. The cDNA encodes a 328 amino acid IGF-binding protein precursor which contains a 39-residue signal peptide. The mature 289 amino acid IGFBP-2 has a predicted Mr of 31,325. Chinese hamster ovary (CHO) cells stably transformed with the IGFBP-2 cDNA secreted a 36 kd protein which bound, with different affinities, IGFII and IGFI, but did not bind insulin. The predicted protein sequence of this IGF-binding protein shares extensive amino acid homology (greater than 85%) with the IGF-binding protein secreted by rat BRL-3A cells, but less than 40% homology with human IGFBP-1. Therefore IGFBP-2, and not IGFBP-1 as previously suggested, represents the human homologue of the rat BRL-BP (alpha IGFBP-2). Moreover, from alignment of the predicted protein sequences of IGFBP-1 and IGFBP-2, extensive conservation of the distribution of cysteine residues is observed. Although the overall amino acid homology shared by these proteins is not high, we suggest that they represent a family of structurally related human IGFBPs. Southern blot analysis of human DNA demonstrates that IGFBP-2 is encoded by a single-copy gene, different from that of IGFBP-1.
Binkert
C
C
Zentrum für Lehre und Forschung, Kantonsspital, Basel, Switzerland.
Landwehr
J
J
Mary
J L
JL
Schwander
J
J
Heinrich
G
G
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics*; D003001:Cloning, Molecular; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D008969:Molecular Sequence Data; D011061:Poly A / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D013002:Somatomedins / Q000378:metabolism*; D014162:Transfection
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D013002:Somatomedins; D011061:Poly A