Nitrate uptake in Aspergillus nidulans and involvement of the third gene of the nitrate assimilation gene cluster.

AUTOR(ES)

Brownlee, A G

RESUMO

In Aspergillus nidulans, chlorate strongly inhibited net nitrate uptake, a process separate and distinct from, but dependent upon, the nitrate reductase reaction. Uptake was inhibited by uncouplers, indicating that a proton gradient across the plasma membrane is required. Cyanide, azide, and N-ethylmaleimide were also potent inhibitors of uptake, but these compounds also inhibited nitrate reductase. The net uptake kinetics were problematic, presumably due to the presence of more than one uptake system and the dependence on nitrate reduction, but an apparent Km of 200 microM was estimated. In uptake assays, the crnA1 mutation reduced nitrate uptake severalfold in conidiospores and young mycelia but had no effect in older mycelia. Several growth tests also indicate that crnA1 reduces nitrate uptake. crnA expression was subject to control by the positive-acting regulatory gene areA, mediating nitrogen metabolite repression, but was not under the control of the positive-acting regulatory gene nirA, mediating nitrate induction.

Documentos Relacionados

• Molecular cloning and functional characterization of the pathway-specific regulatory gene nirA, which controls nitrate assimilation in Aspergillus nidulans.
• Metabolite Repression and Inducer Exclusion in the Proline Utilization Gene Cluster of Aspergillus nidulans
• A third unlinked gene controlling the pyruvate dehydrogenase complex in Aspergillus nidulans.
• Identification and molecular analysis of a third Aspergillus nidulans alcohol dehydrogenase gene.
• Autoregulation of the Synthesis of Nitrate Reductase in Aspergillus nidulans