Aspergillus niger mstA encodes a high-affinity sugar/H+ symporter which is regulated in response to extracellular pH.
A sugar-transporter-encoding gene, mstA, which is a member of the major facilitator superfamily, has been cloned from a genomic DNA library of the filamentous fungus Aspergillus niger. To enable the functional characterization of MSTA, a full-length cDNA was expressed in a Saccharomyces cerevisiae strain deficient in hexose uptake. Uptake experiments using 14C-labelled monosaccharides demonstrated that although able to transport D-fructose ( K(m), 4.5+/-1.0 mM), D-xylose ( K(m), 0.3+/-0.1 mM) and D-mannose ( K(m), 60+/-20 microM), MSTA has a preference for D-glucose (K(m), 25+/-10 microM). pH changes associated with sugar transport indicate that MSTA catalyses monosaccharide/H+ symport. Expression of mstA in response to carbon starvation and upon transfer to poor carbon sources is consistent with a role for MSTA as a high-affinity transporter for D-glucose, D-mannose and D-xylose. Northern analysis has shown that mstA is subject to CreA-mediated carbon catabolite repression and pH regulation mediated by PacC. A. niger strains in which the mstA gene had been disrupted are phenotypically identical with isogenic reference strains when grown on 0.1-60 mM D-glucose, D-mannose, D-fructose or D-xylose. This indicates that A. niger possesses other transporters capable of compensating for the absence of MSTA.
Vankuyk
Patricia A
PA
Molecular Genetics of Industrial Microorganisms. Wageningen University, Dreijenlaan 2, 6703 HA Wageningen, The Netherlands. kuyk@rulbim.leidenuniv.nl
Diderich
Jasper A
JA
MacCabe
Andrew P
AP
Hererro
Oscar
O
Ruijter
George J G
GJ
Visser
Jaap
J
D001234:Aspergillus niger / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport; D050260:Carbohydrate Metabolism; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D012097:Repressor Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D027981:Symporters; D014157:Transcription Factors / Q000378:metabolism
D005656:Fungal Proteins; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; C092394:PacC protein, Aspergillus; D012097:Repressor Proteins; D027981:Symporters; D014157:Transcription Factors; C089820:monosaccharide-hydrogen cotransporter; C071237:CreA protein, Aspergillus nidulans