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Molecular cloning, characterization, and homologous expression of an endochitinase gene from Bacillus thuringiensis serovar morrisoni

The endochitinase gene (chi3023) of Bacillus thuringiensis (Bt) serovar morrisoni strain 3023 was amplified via polymerase chain reaction (PCR) and cloned in Escherichia coli. The ORF of chi3023 (GenBank Accession Number: DQ993175) consists of 2031 nucleotides encoding a 676-residue protein with a calculated molecular mass of 74.5 kDa and a pI value of 6.0. The amino acid sequence of Chi3023 was compared with previously sequenced Bt chitinases and the phylogenetic relationships among them were determined. The deduced N-terminal 34 amino acids of the premature Chi3023 exhibited a typical signal peptide. The E. coli-Bt shuttle vector pHT315 was used for homologous expression of chi3023. Introduction of recombinant pHT315BTC, carrying chi3023 into Bt serovar morrisoni 3023, resulted in a 23-fold increase in endochitinase activity (0.185 U/mg versus 4.256 U/mg).