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KMID : 0545119990090010113
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Journal of Microbiology and Biotechnology
1999 Volume.9 No. 1 p.113 ~ p.118
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Identification of an Embryonic Growth Factor IGF-2 from the Central Nervous System of the Teleost,Flounder,and Its Expressions in Adult Tissues
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Kim Dong-Soo
Kim Young-Tae
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Abstract
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The insulin-like growth factor (IGF) is found in all vertebrates and its type-Ⅱ molecule is regarded as a fundamental embryonic growth factor during development. We have firstly identified, in this study, a cDNA clone corresponding to IGF-Ⅱ (flIGF-Ⅱ) from the adult brain of the teleost, Paralichthys olivaceus. We also examined the tissue expression of flIGF-Ⅱ in several adult tissues by RT-PCR. The flIGF-Ⅱ cDNA contained a complete ORF consisting of 215 amino acids and one stop codon. Its molecular characteristics appear to be similar to the previously identified IGF-Ⅱ molecules, in which ,a common primary structure exhibiting B, C, A, D. and E domains is evidently observed. This cDNA clone seems to he cleaved at Ala^ for the NH-end signal peptide and appears to produce a 98 amino acid-long E-peptide from the Arg^ The functional B∼D domain regions, therefore. include 65 amino acids and is able to encode a 7.4-kDa protein. The most prominent structural difference between IGF-Ⅰ and IGF-Ⅱ was that the D domain of IGF-Ⅱ exhibits a two-codon-deleted pattern compared to the 8 amino acid-containing IGF-Ⅰ. The insulin family signature in the A domain and six cysteins forming three disulfide bridges between the B and A domains were evolutionary-conserved from teleosts to mammalian IGF-Ⅱ. Interestingly, the E-peptide region appears to provide a distinct hallmark between teleosts in amino acid composition. The flIGF-Ⅱ shows 85.1% of sequence identity to salmon and trout. 90.6% to tilapia, and 98.4% to perch in amino acid level. In tissue expressions of IGF-Ⅱ, it is very likely that flIGF-Ⅱ has a significant expression in the adult brain. However, liver seems to be the main source for IGF-Ⅱ production. and relatively low signals were observed in the adult muscle and kidney. Taken together, it would be concluded that the functional region for IGF-Ⅱ mRNA is highly similar in phylogeny and is evolutionary. conserved as a mediator for the growth of vertebrates.
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