Structure and functional expression of the acid-labile subunit of the insulin-like growth factor-binding protein complex.
Nearly all of the insulin-like growth factor (IGF) in the circulation is bound in a heterotrimeric complex composed of IGF, IGF-binding protein-3, and the acid-labile subunit (ALS). Full-length clones encoding ALS have been isolated from human liver cDNA libraries by using probes based on amino acid sequence data from the purified protein. These clones encode a mature protein of 578 amino acids preceded by a 27-amino acid hydrophobic sequence indicative of a secretion signal. Expression of the cDNA clones in mammalian tissue culture cells results in the secretion into the culture medium of ALS activity that can form the expected complex with IGF-I and IGF-binding protein-3. The amino acid sequence of ALS is largely composed of 18-20 leucine-rich repeats of 24 amino acids. These repeats are found in a number of diverse proteins that, like ALS, participate in protein-protein interactions.
Leong
S R
SR
Department of Molecular Biology, Genentech, Inc., South San Francisco, California 94080.
Baxter
R C
RC
Camerato
T
T
Dai
J
J
Wood
W I
WI
D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D016384:Consensus Sequence; D004247:DNA / Q000235:genetics; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D008969:Molecular Sequence Data; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D013002:Somatomedins / Q000378:metabolism*; D013329:Structure-Activity Relationship
D002352:Carrier Proteins; D006023:Glycoproteins; D018969:Insulin-Like Growth Factor Binding Proteins; D011993:Recombinant Fusion Proteins; D013002:Somatomedins; C075944:insulin-like growth factor binding protein, acid labile subunit; D004247:DNA