High-multiplicity of chitinase genes in Streptomyces coelicolor A3(2)

Cloning of a two-component regulatory system probably involved in the regulation of chitinase in Streptomyces coelicolor A3(2)

Using the method for the identification of promoters recognized by the sporulation specific sigma factor (sigma F), we identified a positive 950 bp Sau3AI DNA fragment in Streptomyces coelicolor A3(2). High-resolution S1-nuclease mapping identified a potential promoter, PF35, in the E. coli two-plasmid system similar to the consensus sequence of Bacillus subtilis promoters recognized by the general stress-response sigma factor (sigma B). However, the putative sigF-dependent promoter, PF35, was inactive in S. coelicolor in the course of differentiation, and it was located divergently in the promoter region directing expression of the chiC gene encoding chitinase. Sequence analysis of the region potentially governed by PF35 revealed two translationally coupled genes encoding proteins similar to bacterial two-component regulatory systems, and with the highest similarity to the two-component system chiS, chiR, regulating chitinase activity in Streptomyces thermoviolaceus. However, the genes had a divergent orientation with respect to the PF35 promoter. Disruption of the S. coelicolor chiR gene appeared to have no obvious effect on growth, morphology, differentiation, and production of pigmented antibiotic actinorhodin and undecylprodigiosin. Moreover, the chiR disruption did not affect the overall chitinase activity.

Family 19 chitinases of Streptomyces species: characterization and distribution

Chitinase C from Streptomyces griseus HUT6037, described in 1997, is the first family 19 chitinase found in an organism other than higher plants. In this study, some properties of chitinase C were compared with those of family 18 bacterial chitinases, and the distribution of family 19 chitinases in Streptomyces species was investigated. The specific hydrolysing activity of chitinase C against soluble and insoluble chitinous substrates was markedly higher than those of bacterial family 18 chitinases. Chitinase C exhibited marked antifungal activity, whereas the other bacterial chitinases examined had no antifungal activity. Chitinase C was insensitive to allosamidin, whereas the family 18 bacterial chitinases were sensitive. Taking advantage of this insensitivity to allosamidin, a search was made for family 19 chitinases in various Streptomyces species. Chitinases insensitive to allosamidin were detected in the culture supernatants of all tested Streptomyces species. Southern hybridization analysis using a labelled DNA fragment corresponding to the catalytic domain of chitinase C strongly suggested that these species have genes similar to the chiC gene of S. griseus HUT6037. DNA fragments corresponding to the major part of the catalytic domains were amplified by PCR. The amplified fragments encoded amino acid sequences very similar to that of the corresponding region of chitinase C. Therefore, it was concluded that Streptomyces species generally possess family 19 chitinases which are very similar to chitinase C. Comparison of their amino acid sequences with those of plant family 19 chitinases revealed that Streptomyces family 19 chitinases are class IV type in terms of the presence and positions of deletions of amino acid sequences which are characteristic of plant class IV chitinases.