Abstract：Follistatin inhibits the biological action of several TGF-β family members and promotes muscle growth. In this research largemouth bass Follistatin cDNA was isolated. First, total RNA was isolated from ovary of adult female largemouth bass, and then used to clone the Follistatin cDNA by using RT-PCR and rapid cDNA end amplification. The sequence analysis results showed that the full-length of largemouth bass Follistatin was 1444 bp with an open reading frame(ORF) of 966 bp. The deduced ORF amino acid sequence contained a putative signal peptide of 31 amino acids and a mature peptide of 290 amino acids that was composed of four domains including N-domain, DomainⅠ, Domain Ⅱand Domain Ⅲ. Comparing Follistatin mature peptide of largemouth bass with those of torafugu, grass carp, zebrafish, Atlantic salmon and channel catfish, the results showed that the amino acid homology is 97％, 89％, 88％, 88％ and 70％, respectively. Follistatin protein binds with several TGF-β family members through its N-domain. Comparing Follistatin N-domain of largemouth bass with those of torafugu, grass carp, zebrafish, Atlantic salmon and channel catfish, African clawed toad, human, pig, rat and chicken, the results showed that the amino acid homology is 75%~100％. It was clear that the sequences of N-domain showed more conservation than those of mature peptide, which suggested that it was highly restricted in the process of evolution and its functional importance. In order to gain Follistatin fusion protein, Follistatin mature peptide cDNA was inserted into pET-32a(+) vector, which was transformed into BL21 and induced by IPTG. Expression products were detected by SDS-PAGE and confirmed by Western blotting analysis, which showed that the molecule weight of Follistatin fusion protein was about 52kD. This study will benefit further researching of Follistatin promoting muscle growth.
