Characterization and expression of the Neurospora crassa nmt-1 gene

The Neurospora crassa homologue of the yeast no message in thiamine ( nmt-1) gene was characterized. The deduced 342-amino-acid gene product has more than 60% identity with other fungal homologues and 42% similarity to a putative bacterial permease. In addition to three introns disrupting the coding...

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Bibliographic Details
Published in:Current genetics 2003-12, Vol.44 (4), p.216-223
Main Authors: McColl, Dorothy, Valencia, C Alexander, Vierula, P John
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Base Sequence
Biosynthesis
Chromosome Mapping
DNA, Complementary - genetics
Fungi
Gene Expression Regulation, Fungal
Immunoblotting
Molecular Sequence Data
Mutation - genetics
Neurospora crassa
Neurospora crassa - genetics
Neurospora crassa - growth & development
nmt-1 gene
NMT-1 protein
Polymorphism, Restriction Fragment Length
RNA, Messenger - metabolism
Schizosaccharomyces pombe Proteins - genetics
Schizosaccharomyces pombe Proteins - metabolism
Sequence Analysis, DNA
thiamine
Thiamine - metabolism
Yeasts
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Summary:The Neurospora crassa homologue of the yeast no message in thiamine ( nmt-1) gene was characterized. The deduced 342-amino-acid gene product has more than 60% identity with other fungal homologues and 42% similarity to a putative bacterial permease. In addition to three introns disrupting the coding sequence, a differentially spliced intron in the 5' untranslated region was also detected. Unlike other fungi, the N. crassa nmt-1 gene is repressed only 6- to 8-fold by exogenous thiamine concentrations above 0.5 microM; and a high basal level of nmt-1 mRNA persists even at 5 microM thiamine. Immuno-blotting with purified antibodies detected two variants of NMT-1 which differ in size and charge. The more abundant 39-kDa form is more strongly repressed by thiamine than the 37-kDa protein. NMT-1 abundance modulates slowly in response to changes in the concentration of exogenous thiamine, suggesting that N. crassa maintains thiamine reserves in excess of immediate needs. Disruption of the nmt-1 gene demonstrated that it is essential for growth in the absence of exogenous thiamine. NMT-1-deficient strains had a growth rate and colony density which was about 70% of the wild type, despite supplementation with a wide range of exogenous thiamine. These results suggest that the nmt-1 gene plays some other role in addition to thiamine biosynthesis.
ISSN:0172-8083
1432-0983
DOI:10.1007/s00294-003-0441-0