Salmon serum 22 kDa insulin-like growth factor-binding protein (IGFBP) is IGFBP-1
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概要
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Western ligand blotting of salmon serum typically reveals three insulin-like growth factor binding proteins (IGFBPs) at 22, 28 and 41 kDa. Physiological regulation of the 22-kDa IGFBP is similar to that of mammalian IGFBP-1; it is increased under catabolic states such as fasting and stress. On the other hand, its molecular weight on Western ligand blotting is closest to mammalian IGFBP-4. The conflict between physiology and molecular weight makes it difficult to conclude the identity of the 22-kDa IGFBP. This study therefore aimed to identify the 22-kDa IGFBP based on protein and cDNA sequences. The 22-kDa IGFBP was purified from Chinook salmon serum by a combination of IGF-affinity chromatography and reverse-phase chromatography. N-terminal amino acid sequence of the purified protein was used to design degenerate primers. Degenerate polymerase chain reaction (PCR) with liver template amplified a partial IGFBP cDNA, and full length cDNA was obtained by 5'- and 3'-rapid amplification of cDNA ends (RACE). The 1915-bp cDNA clone encodes a 23.8 kDa IGFBP and its N-terminal amino acid sequence matched that of purified 22-kDa IGFBP. Sequence comparison with six human IGFBPs revealed that it is most similar to IGFBP-1 (40% identity and 55% similarity). These findings indicate that salmon 22-kDa IGFBP is IGFBP-1. Salmon IGFBP-1 mRNA is predominantly expressed in the liver and its expression levels appear to reflect circulating levels. The 3'-untranslated region of salmon IGFBP-1 mRNA contains four repeats of the nucleotide sequence ATTTA, which is involved in selective mRNA degradation. In contrast, amino acid sequence analysis revealed that salmon IGFBP-1 does not have an Arg-Gly-Asp (RGD) integrin recognition sequence nor a Pro, Glu, Ser and Thr (PEST) rich domain (a segment involved in rapid turnover of protein), both of which are characteristics of mammalian IGFBP-1. These findings suggest that association with the cell surface and turnover rate may differ between salmon and mammalian IGFBP-1.
- Society for Endocrinologyの論文
Society for Endocrinology | 論文
- Measurement of circulating salmon IGF binding protein-1 : assay development, response to feeding ration and temperature, and relation to growth parameters
- Salmon serum 22 kDa insulin-like growth factor-binding protein (IGFBP) is IGFBP-1