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Isolation and characterization of ovine IGFBP-4: protein purification and cDNA sequence

Version 2 2024-06-05, 02:02
Version 1 2019-01-16, 14:59
journal contribution
posted on 2024-06-05, 02:02 authored by JM Carr, PA Grant, GL Francis, Julie OwensJulie Owens, JC Wallace, PE Walton
Three different molecular mass forms of IGF-binding proteins (IGFBPs) were purified from ovine plasma by IGF-I affinity chromatography and reverse-phase HPLC: a 46 kDa doublet and 29 kDa and 24 kDa forms. Amino-terminal sequence analysis confirmed that these proteins were ovine (o)IGFBP-3 (46 kDa) and two molecular size variants of oIGFBP-4. oIGFBP-3 and the 29 kDa form of oIGFBP-4 were shown to be N-glycosylated. Isoelectric points were determined to be at approximately pH 6 for oIGFBP-3 and at pH 7 and pH 7.5 for the 29 and 24 kDa forms of oIGFBP-4 respectively. The two different molecular mass variants of oIGFBP-4 had similar IGF-binding properties. Compared with human IGFBP-3 and oIGFBP-3, the two variants of oIGFBP-4 exhibited lower relative binding to amino-terminally modified IGF-I analogues in a competitive IGF-binding assay. The full protein sequence of oIGFBP-4, as deduced from the cDNA sequence, showed a high degree of identity with rat (90%), human (96%) and bovine (98%) IGFBP-4. The cDNA sequence also showed homology over regions of the 3' non-coding sequence, particularly in comparison with bovine IGFBP-4 (96%). Northern analysis of mRNA for oIGFBP-4 indicated a 2.6 kb major transcript and two minor transcripts of approximately 2.1 and 1.8 kb. oIGFBP-4 mRNA transcripts were detected in adult ewe liver > kidney > lung > heart and also in several fetal tissues, thus suggesting tissue-specific and developmental regulation. The availability of purified oIGFBP-4 and oIGFBP-3 as well as DNA probes for oIGFBP-4 will enable further study of the properties and functions of these proteins, as well as the establishment of specific assays for these IGFBPs.

History

Journal

Journal of molecular endocrinology

Volume

13

Pagination

219-236

Location

Bradley Stok, Eng.

ISSN

0952-5041

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

1994, Bioscientifica

Issue

2

Publisher

Bioscientifica