Purification, amino acid sequences and assay cross-reactivities of porcine insulin-like growth factor-I and -II.
Porcine insulin-like growth factor-I (IGF-I) and IGF-II have been characterized to help define the roles of these peptides in the growth process. The amino acid sequence of porcine IGF-I was found to be identical to the human and bovine peptides. Porcine IGF-II was more similar to human IGF-II than to forms of this growth factor in other mammalian species, differing only in the replacement of asparagine for serine at residue 36. In a biological assay that measures the stimulation of protein synthesis in rat L6 myoblasts, porcine IGF-I was approximately ninefold more potent than porcine IGF-II or bovine IGF-II, while recombinant human IGF-I and IGF-II had half the potency of the respective natural peptides. Porcine and recombinant human IGF-I showed essentially equal competition for binding in a human IGF-I radioimmunoassay while between 0.6 and 1.5% cross-reactivity was observed with human, bovine or porcine IGF-II. A receptor assay for IGF-II demonstrated similar potencies for the three IGF-II peptides, while the cross-reactivity of recombinant human IGF-I was only 0.05%. Porcine IGF-I exhibited a higher cross-reactivity, presumably due to very slight contamination with IGF-II.
Francis
G L
GL
CSIRO Division of Human Nutrition, Adelaide, South Australia.
Owens
P C
PC
McNeil
K A
KA
Wallace
J C
JC
Ballard
F J
FJ
D000595:Amino Acid Sequence; D000818:Animals; D003429:Cross Reactions; D007334:Insulin-Like Growth Factor I / Q000302:isolation & purification*; D007335:Insulin-Like Growth Factor II / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000096:biosynthesis; D011863:Radioimmunoassay; D011869:Radioligand Assay; D051381:Rats; D013002:Somatomedins / Q000302:isolation & purification*; D013552:Swine
D009124:Muscle Proteins; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II