Cloning, Sequencing and Expression of Goonch Bagarius bagarius (Hamilton, 1822) Growth Hormone

Abstract Goonch Bagarius bagarius (Hamilton, 1822) is one of the largest and fastest-growing catfish of the Indus River found at Taunsa Barrage, Pakistan. The full-length cDNA of the growth hormone gene (600 bp) was amplified by reverse transcription of mRNA isolated from the pituitary gland of B. bagarius . The full-length growth hormone gene encodes a putative polypeptide of 200 amino acids with a molecular mass of 22.58 kDa. The precursor of B. bagarius growth hormone (GH) is composed of 22 amino acids as a signal peptide and 178 amino acids of a mature peptide. There were six conserved Cys residues in GH protein (20, 71, 135, 173, 190 and 198) that maintain the structural integrity of this protein. One putative N-glycosylation site was present at the 197 th amino acid. The total number of positively charged (Arg and Lys) and negatively charged (Asp and Glu) residues is 42 and 31, respectively. The B. bagarius GH gene shows more than 90% sequence homology with other catfishes. The mature protein GH gene was expressed in Escherichia coli using pET-28 expression vector, and the recombinant protein of 19.5 kDa was detected through SDS-PAGE analysis. This study suggests that cloning and expression of B. bagarius GH gene would provide basic information for transgenic studies aimed at a faster growth rate. This recombinant GH may be produced on a large scale to exploit its growth-promoting function in other cultured fishes.