Purification, partial sequences and properties of chicken insulin-like growth factors.
Insulin-like growth factor-I (IGF-I) and IGF-II have been purified to homogeneity from chicken serum as a step towards the characterization of the roles for these peptides in the growth process. Chicken IGF-I had about half the efficacy of bovine/human IGF-I in a bioassay and in radioimmunoassays with bovine IGF-I as radioligand. Chicken IGF-II competed for the binding of bovine IGF-II to cell receptors while chicken IGF-I reacted minimally in this IGF-II radioreceptor assay. Further evidence of homology was obtained by N-terminal sequence analysis of the first 31 and 35 amino acids of chicken IGF-I and IGF-II respectively. Chicken IGF-I had the same N-terminal as human IGF-I, with the exception of the substitution of serine for asparagine at residue 26. Chicken IGF-II had a unique N-terminal tetrapeptide Tyr-Gly-Thr-Ala, but from residues 5-30 the sequence was identical to that reported for residues 6-31 of human IGF-II. Substitutions also occurred corresponding to residues 32, 33, 35 and 36 of human IGF-II. A variant form of chicken IGF-II that had the same N-terminal pentapeptide as human IGF-II was also detected.
Dawe
S R
SR
CSIRO Division of Human Nutrition, Adelaide, Australia.
Francis
G L
GL
McNamara
P J
PJ
Wallace
J C
JC
Ballard
F J
FJ
D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D003429:Cross Reactions; D007334:Insulin-Like Growth Factor I / Q000302:isolation & purification* / Q000502:physiology; D007335:Insulin-Like Growth Factor II / Q000302:isolation & purification* / Q000502:physiology; D008969:Molecular Sequence Data; D013002:Somatomedins / Q000302:isolation & purification*
D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II