Objective: We identified a microbial transglutaminase (MTGase) gene from Streptomyces hygroscopicus; cloned and expressed it in Escherichia coli. We also analyzed the active sites sequence of S. hygroscopicus MTGase through homologous sequence comparison.
Methods: Wild-type microbial transglutaminase zymogen (pro-MTGase) was purified from liquid culture of S. hygroscopicus (CCTCC M203062). N-terminal amino acid sequence of this pro-MTGase was determined. According to the N-terminal sequence and the corresponding nucleotide sequence of MTGase from other three Streptomyces species, PCR primers of S. hygroscopicus pro-MTGase were designed and the completed gene of pro-MTGase was amplified and sequenced. The gene was sub-cloned into pET-20b(+) vector downstream pelB signal peptide to construct the expression vector pET/pro-MTG.
Results: The nucleotide sequence showed 92% homologue with that of S. platensis and S. caniferus. Rosetta (DE3) pLysS carrying the expression vector was induced with IPTG at 24 and expressed pro-MTGase as extracellular soluble protein. SDS-PAGE showed the expressed recombinant pro-MTGase was about 44 kDa, similar to the wild-type pro-MTGase purified from S. hgroscopicus. Recombinant pro-MTGase was activated with trypsin and the enzyme activity reached to 0.24U/mL.
Conclusion: This is the first report of the gene encoding microbial pro-transglutaminase from S. hygroscopicus, and also this is the first report of expression extracellular soluble pro-MTGase in E. coli in our country.