Calderón Jorge, Olvera Leticia, Martínez Luz María, Dávila Guillermo
Departamento de Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México DF 04510, Mexico.
Departamento de Ecología Molecular, Centro de Investigación sobre Fijación de Nitrógeno UNAM, Apartado Postal 565-A, Cuernavaca, Mor., Mexico.
Microbiology (Reading). 1997 Jun;143 ( Pt 6):1969-1974. doi: 10.1099/00221287-143-6-1969.
The isolation and characterization of a Neurospora crassa mutant altered in L-amino oxidase regulation is reported. The previously isolated gln-1bR8 strain, which only synthesizes the glutamine synthetase alpha monomer and lacks the beta monomer, was used as parental strain. A mutant derivative of strain was selected for its ability to grow on minimal medium in the presence of DL-methionine-SR-sulfoximine (MSO), an inhibitor of glutamine synthetase activity. This gln-1bR8;MSOR mutant overcame the inhibitory effect of MSO by increasing the activity of L-amino acid oxidase, an enzyme capable of degrading this compound. In contrast with the wild-type strain, the L-amino acid oxidase of the MSOR mutant was resistant to glutamine repression; in fact, it was induced by this amino acid but repressed by ammonium. This mutant is different from other nitrogen regulatory N. crassa mutants reported and is only altered in the regulation of L-amino acid oxidase. The MSOR mutation is epistatic to nit-2 since the nit2;MSOR double mutant regulated the L-amino acid oxidase in the same way as the MSOR single mutant.
