The Aspergillus nidulans metZ gene encodes a transcription factor involved in regulation of sulfur metabolism in this fungus and other Eurotiales.

In Aspergillus nidulans, expression of sulfur metabolism genes is activated by the MetR transcription factor containing a basic region and leucine zipper domain (bZIP). Here we identified and characterized MetZ, a new transcriptional regulator in A. nidulans and other Eurotiales.

Regulatory mutations affecting sulfur metabolism induce environmental stress response in Aspergillus nidulans.

Mutations in the cysB, sconB and sconC genes affect sulfur metabolism in Aspergillus nidulans in different ways. The cysB mutation blocks synthesis of cysteine by the main pathway and leads to a shortage of this amino acid. The sconB and sconC mutations affect subunits of the SCF ubiquitin ligase complex, which inactivates the MetR transcription factor in the presence of an excess of cysteine.

Novel mutations reveal two important regions in Aspergillus nidulans transcriptional activator MetR.

Expression of the sulfur assimilation pathway in Aspergillus nidulans is under control of sulfur metabolite repression, which is composed of scon genes encoding subunits of ubiquitin ligase and the metR gene coding for a transcriptional activator. In this paper we report three dominant suppressors of methionine requirement isolated from a metB3 diploid strain. All three mutations lead to the substitution of phenylalanine 48 by serine or leucine in the conserved N-terminal region of the MetR protein.

Sulfate permeasesphylogenetic diversity of sulfate transport.

Sulfate uptake, the first step of sulfate assimilation in all organisms, is a highly endoergic, ATP requiring process. It is under tight control at the transcriptional level and is additionally modulated by posttranslational modifications, which are not yet fully characterized. Sulfate anion is taken up into the cell by specific transporters, named sulfate permeases, located in the cell membrane.

Aspergillus nidulans genes encoding reverse transsulfuration enzymes belong to homocysteine regulon.

Homocysteine is an intermediate in methionine synthesis in Aspergillus nidulans, but it can also be converted to cysteine by the reverse transsulfuration pathway involving cystathionine beta-synthase (CBS) and cystathionine gamma-lyase (CGL). Because homocysteine is toxic to the cell at high concentrations, this pathway also functions as a means of removal of its excess. We found that the transcription of the mecA and mecB genes encoding CBS and CGL was upregulated by excess of homocysteine as well as by shortage of cysteine.