Molecular characterization of a novel chitinase from Bacillus thuringiensis subsp. kurstaki

Aims:  The present work aims to study a new chitinase from Bacillus thuringiensis subsp. kurstaki. Methods and Results:  BUPM255 is a chitinase-producing strain of B. thuringiensis, characterized by its high chitinolytic and antifungal activities. The cloning and sequencing of the corresponding gene named chi255 showed an open reading frame of 2031 bp, encoding a 676 amino acid residue protein. Both nucleotide and amino acid sequences similarity analyses revealed that the chi255 is a new chitinase gene, presenting several differences from the published chi genes of B. thuringiensis. The identification of chitin hydrolysis products resulting from the activity, exhibited by Chi255 through heterologous expression in Escherichia coli revealed that this enzyme is a chitobiosidase. Conclusions:  Another chitinase named Chi255 belonging to chitobiosidase class was evidenced in B. thuringiensis subsp. kurstaki and was shown to present several differences in its amino acid sequence with those of published ones. The functionality of Chi255 was proved by the heterologous expression of chi255 in E. coli. Significance and Impact of the Study:  The addition of the sequence of chi255 to the few sequenced B. thuringiensis chi genes might contribute to a better investigation of the chitinase ‘structure-function’ relation.