[cDNA cloning and protein structure analysis of growth hormone from Clarias lazera]

Total RNA was isolated from pituitary gland of Clarias lazera, and the cDNA encoding growth hormone (GH) protein was amplified and cloned by reverse transcription polymerase chain reaction (RT-PCR). The open reading frame (ORF) of cDNA is of 603 nt which encodes GH precursor consisted of a signal peptide with 22 amino acid residues and a mature peptide with 178 amino acid residues. Sequence alignment indicated that the amino acid sequence homology approached to 95.8% between C. lazera and other 6 species of Siluriforms catfish. Secondary structure assessment showed that the GH protein contained different structural regions of alpha-helix, beta-sheet, beta-turn and random coil, among which alpha-helix has main proportion. Antigenicity analysis indicates that there exist 4 domains in amino acid sequence where B cell dominant epitopes could form. Summarily, the structure characteristics of C. lazera GH should provide a great benefit in its modification into recombinant vaccine or monoclonal antibody for future application.