Cloning of the xylanase gene of Streptomyces lividans

Abstract

The xylanase ( xln) gene of Streptomyces lividans 1326 was cloned by functional complementation of the xylanase-negative and β-1,4-glucan-glucanohydrolase-negative double mutant of S. lividans using the multicopy plasmid pIJ702. Three clones had a common 2-kb DNA fragment as determined by restriction mapping and Southern hybridization. These clones secreted a xylanase of M r 43 000 which reacted with specific antixylanase antibodies and corresponded exactly to the enzyme previously isolated from the wild-type strain. The DNA fragment likely carried the full structural gene, the xln promoter and also the regulatory sequence, since the xylanase activity was inducible by xylan. Enzyme levels of up to 380 IU/ml of culture filtrate were obtained.