Characterization of a polygalacturonase gene of Aspergillus niger RH5344

We have cloned a gene encoding a polygalacturonase (PG) in the filamentous fungus Aspergillus niger RH5344. The structural gene comprises 1141 bp coding for 362 amino acids and the open reading frame is disrupted by one intron of 52 bp. Eukaryotic consensus sequences for transcription regulation are found only in deviated forms. The biological functionality of the isolated PG gene was established by retransformation in A. niger and Aspergillus awamori. In addition, we have found that the PG protein of A. niger shares significant similarities with PG proteins from tomato and Erwinia carotovora. Comparison of the three enzymes revealed a highly conserved region in their C-terminal region probably comprising the elements of substrate binding and the catalytic centre.