THE CATR GENE ENCODING A CATALASE FROM ASPERGILLUS-NIGER - PRIMARY STRUCTURE AND ELEVATED EXPRESSION THROUGH INCREASED GENE COPY NUMBER ANDUSE OF A STRONG PROMOTER

Synthetic oligonucleotide probes based on amino acid sequence data wer e used to identify and clone cDNA sequences encoding a catalase (catal ase-R) of Aspergillus niger. One cDNA clone was subsequently used to i solate the corresponding genomic DNA sequences (designated catR). Nucl eotide sequence analysis of both genomic and cDNA clones suggested tha t the catR coding region consists of five exons interrupted by four sm all introns. The deduced amino acid sequence of catalase-R spans 730 r esidues which show significant homology to both prokaryotic and eukary otic catalases, particularly in regions involved in catalytic activity and binding of the haem prosthetic group. Increased expression of the catR gene was obtained by transformation of an A. niger host strain w ith an integrative vector carrying the cloned genomic DNA segment. Sev eral of these transformants produced three- to fivefold higher levels of catalase than the untransformed parent strain. Hybridization analys es indicated that these strains contained multiple copies of catR inte grated into the genome. A second expression vector was constructed in which the catR coding region was functionally joined to the promoter a nd terminator elements of the A. niger glucoamylase (glaA) gene. A. ni ger transformants containing this vector produced from three- to 10-fo ld higher levels of catalase-R than the untransformed parent strain.