title: Isolation and characterization of mutants of Aspergillus niger deficient in extracellular proteases.
abstract: In the present study, the extracellular protease activity in a strain of the filamentous fungus Aspergillus niger was investigated and mutant strains deficient in the production of extracellular proteases were isolated. The major protease, which is responsible for 80-85% of the total activity, is aspergillopepsin A, a protein of ca. 43 kDa, the activity of which is inhibited by pepstatin. In addition, a second protease, aspergillopepsin B, is produced, which is much less sensitive to inhibition by pepstatin. Several protease-deficient mutants were obtained by in vivo UV mutagenesis. In addition, a mutant lacking aspergillopepsin A was constructed by an in vitro gene replacement strategy. In this mutant, AB1.1, the entire coding region of the gene for aspergillopepsin A (pepA) is deleted. In three UV-induced mutants, aspergillopepsin A is also missing. One of these mutants, AB1.18, is mutated in the pepA gene, which is located on chromosome I. One of the other mutants, AB1.13, which has only 1-2% of the extracellular protease activity in the parent strain, is deficient in both aspergillopepsin A and aspergillopepsin B. The mutation involved, prt-13, has been localized to chromosome VI, and is probably a mutation in a regulatory gene. Another mutation involved in loss of protease function, prt-39, is located on chromosome VIII. Degradation of various heterologous proteins in culture media of the mutants is reduced but, even in strain AB1.13, not completely abolished.
authors.affiliation: TNO Medical Biological Laboratory, Rijswijk, The Netherlands.
authors.forename: I E
authors.initials: IE
authors.lastname: Mattern
authors.forename: J M
authors.initials: JM
authors.lastname: van Noort
authors.forename: P
authors.initials: P
authors.lastname: van den Berg
authors.forename: D B
authors.initials: DB
authors.lastname: Archer
authors.forename: I N
authors.initials: IN
authors.lastname: Roberts
authors.forename: C A
authors.initials: CA
authors.lastname: van den Hondel
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000235:genetics* / Q000378:metabolism; D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D015153:Blotting, Western; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D016296:Mutagenesis / Q000235:genetics
chemical_list: D005656:Fungal Proteins; D016282:Aspartic Acid Endopeptidases; C029094:aspergillopepsin I