MOLECULAR CLONING AND SEQUENCE ANALYSIS OF INSULIN-LIKE GROWTH FACTOR IcDNA FROM LARIMICHTHYS CROCEA

The insulin-like growth factor (IGF-Ⅰ) gene of Larimichthys crocea was cloned from liver by RT-PCR and RACE technique. All the length of the nucleotide sequence was 2027bp, including 5’UTR (57bp), 3’UTR (1409bp) and ORF (561bp). Nucleotide sequence analysis showed that ORF encoded 186 amino acids that was composed of signal peptide, mature peptide (B, C, A, D) and E domain. Signal peptide and E domain were cut off when the peptide was processed. The molecular weight of mature peptide was 7500Da and its pI was 7.76. There were three disulfide bonds formed by six cysteines in B and A domains. The disulfide bonds comparing the amino acid sequence of IGF-Ⅰof L. crocea with those of other species, the sequence conservation of A and B domains is high, while low in C and D domains. E domains in IGF-Ⅰ of L. crocea was belonged to IGF-ⅠEa-4 subtype. Analysis of nucleotide sequence showed that IGF-ⅠcDNA of L. crocea is similar to other fishes which shared sequence homology of 99.47% with Sciaenops ocellatus, 97.68% with Epinephelus coioides, 97.50% with Sparus aurata and 95.90% with Paralichthys olivaceus.