Purification, amino acid sequence and characterisation of kangaroo IGF-I.
Insulin-like growth factor-I (IGF-I) and IGF-II have been purified to homogeneity from kangaroo (Macropus fuliginosus) serum, thus this represents the first report of the purification, sequencing and characterisation of marsupial IGFs. N-Terminal protein sequencing reveals that there are six amino acid differences between kangaroo and human IGF-I. Kangaroo IGF-II has been partially sequenced and no differences were found between human and kangaroo IGF-II in the 53 residues identified. Thus the IGFs appear to be remarkably structurally conserved during mammalian radiation. In addition, in vitro characterisation of kangaroo IGF-I demonstrated that the functional properties of human, kangaroo and chicken IGF-I are very similar. In an assay measuring the ability of the proteins to stimulate protein synthesis in rat L6 myoblasts, all IGF-I proteins were found to be equally potent. The ability of all three proteins to compete for binding with radiolabelled human IGF-I to type-1 IGF receptors in L6 myoblasts and in Sminthopsis crassicaudata transformed lung fibroblasts, a marsupial cell line, was comparable. Furthermore, kangaroo and human IGF-I react equally in a human IGF-I RIA using a human reference standard, radiolabelled human IGF-I and a polyclonal antibody raised against recombinant human IGF-I. This study indicates that not only is the primary structure of eutherian and metatherian IGF-I conserved, but also the proteins appear to be functionally similar.
Yandell
C A
CA
Cooperative Research Centre for Tissue Growth and Repair, Adelaide, Australia.
Francis
G L
GL
Wheldrake
J F
JF
Upton
Z
Z
D000595:Amino Acid Sequence; D000704:Analysis of Variance; D000818:Animals; D001681:Biological Assay; D002645:Chickens; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007614:Macropodidae / Q000378:metabolism*; D008969:Molecular Sequence Data; D011863:Radioimmunoassay; D011869:Radioligand Assay; D012474:Salmon; D017386:Sequence Homology, Amino Acid
D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II