Purification, partial sequences and properties of chicken insulin-like growth factors

Abstract

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.

Insulin‐like growth factors I and II

“…IGF I in all six species consists of 70 amino acid residues, IGF I1 of 67, all being grouped into domains A and B (similar to insulin), C (analogous to the connecting peptide of proinsulin) and D (not present in insulins). Chicken IGF I and I1 have only been partially sequenced [65].…”

Hepatic mRNA expression and plasma levels of insulin-like growth factor-I (IGF-I) in broiler chickens selected for different growth rates

“…Insulin-like growth factor-I (IGF-I) is a highly conserved, 70 amino acid, single-chain polypeptide that plays an important role in the control of growth and metabolism in chickens and mammals (Dawe et al, 1988;Florini et al, 1996). Growth and differentiation are stimulated when exogenous IGF-I is injected into chicken embryos (Girbau et al, 1987), but after hatching, the gene expression and plasma concentration of IGF-I increase with age and then decline between 6 and 7 weeks of age (Huybrechts et al, 1985;Johnson et al, 1990;McGuinness and Cogburn, 1990).…”

Purification, amino acid sequence and characterisation of kangaroo IGF-I

“…IGF proteins or cDNA transcripts have been described in the chicken (Dawe et al 1988, Kallincos et al 1990, several species of fish (Cao et al 1989, Duguay et al 1995, 1996, Moriyama et al 1995, Liang et al 1996, Kinhult 1996 and the frog, Xenopus laevis (Kajimoto & Rotwein 1990). N-Terminal protein sequencing and the cDNA-deduced amino acid sequences indicate that there is a high degree of conservation of IGF structure throughout vertebrate evolution.…”

“…However, the role of IGFs in these species has not been extensively characterised and it remains to be determined if IGFs have been functionally as well as structurally conserved throughout vertebrate evolution. While in vitro characterisation of salmon (Moriyama et al 1993), trout (Moriyama et al 1995) and chicken (Dawe et al 1988, Armstrong et al 1990, Kallincos et al 1990, Upton et al 1992) IGF-I has been described, very few in vivo studies using homologous proteins have been performed. Marsupials (metatherians) diverged most recently from placental mammals (eutherians) and are thought to have potential as developmental models (Tyndale-Biscoe & Janssens 1988).…”