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The acetamidase of Mycobacterium smegmatis is an inducible enzyme which enables the organism to utilise several amides as sole carbon sources. The acetamidase structural gene (amiE) is located downstream of four other genes, of which three form a probable operon with amiE; the fourth (amiC) is divergently transcribed. We constructed deletion mutants in two of these genes in order to determine their role in acetamidase expression. Both AmiC and AmiD were shown to be positive regulators of acetamidase expression required for induction. Combinations of regulatory gene deletions were made which revealed that AmiC interacts with the previously characterised negative regulator AmiA, whereas AmiD does not. 相似文献
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Sarah S. Gonçalves Josep F. Cano Alberto M. Stchigel Analy S. Melo Patricio C. Godoy-Martinez Benedito Correa Josep Guarro 《Fungal biology》2012,116(11):1146-1155
Aspergillus flavus is the second most common cause of aspergillosis infection in immunocompromised patients and is responsible for the production of aflatoxins. Little is known about the population structure of A. flavus, although recent molecular and phenotypic data seem to demonstrate that different genetic lineages exist within this species. The aim of this study was to carry out a morphological, physiological, and molecular analysis of a set of clinical and environmental isolates to determine whether this variability is due to species divergence or intraspecific diversity, and to assess whether the clinical isolates form a separate group. The amdS and omtA genes were more phylogenetically informative than the other tested genes and their combined analysis inferred three main clades, with no clear distinction between clinical and environmental isolates. No important morphological and physiological differences were found between the members of the different clades, with the exception of the assimilation of d-glucosamine, which differentiates the members of the clade II from the others. 相似文献
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Nathalie Bonnefoy Jane Copsey Michael J. Hynes Mervl A. Davis 《Molecular & general genetics : MGG》1995,246(2):223-227
The upstream regulatory region of the amdS gene of Aspergillus nidulans contains a CCAAT sequence known to be important in setting both basal and derepressed levels of expression. We have investigated whether the CCAAT-binding HAP2/3/4 complex of the yeast Saccharomyces cerevisiae can recognise this sequence in an amdS context. Sequences from the 5 region of amdS were cloned in front of the CYCI-lacZ fusion gene bearing a minimal promoter and transformed into wild-type and hap2 strains of yeast. This study has indicated that amdS sequences are capable of promoting regulated expression of the fusion gene in response to carbon limitation. The yeast HAP2/3/4 complex can recognise the amdS CCAAT sequence and activate expression from this sequence. In addition, the results indicate that other yeast proteins can also regulate expression from the A. nidulans amdS 5 sequences under carbon-limiting conditions. 相似文献
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Peter M. Gresshoff 《Archives of microbiology》1981,128(3):303-306
Chlamydomonas reinhardi can utilise the lower aliphatic amides (C1–C4) as nitrogen sources. Of these only acetamide can serve as a sole carbon source. The acetamide analogue F-acetamide kills cells after conversion to F-acetate and F-citrate. This conversion is controlled by exogenous ammonia and, in part, acetate levels. Only one enzyme and one active site are involved in acetamidase function. Enzymatic analysis indicates an increased substrate range as compared to the growth — supported range, indicating uptake, toxicity or metabolic control restrictions.Abbreviations TCA
trichloroacetic acid
- TAP
tris-acetate-phosphate medium
- MIC
mimmum inhibitory concentration
- BSA
bovine serum albumin 相似文献
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Carl T. Yamashiro Oded Yarden Charles Yanofsky 《Molecular & general genetics : MGG》1992,236(1):121-124
Summary When Neurospora crassa is transformed using a Neurospora gene as the selectable marker, the vegetatively stable transformants obtained cannot be used successfully in a cross because the selectable marker will be inactivated by the process of RIP (repeat-induced point mutation). Introduction of the acetamidase-encoding gene amdS of Aspergillus nidulans into N. crassa by transformation yielded transformants that would grow in minimal medium containing acetamide as a sole nitrogen source. In mitotically stable transformants containing a single copy of the amdS gene, the capacity to utilize acetamide as a sole nitrogen source was maintained in the progeny of a sexual cross. Therefore, the A. nidulans amdS gene is an appropriate dominant selectable marker for use in transformation analyses with N. crassa in which sexual crosses will be subsequently performed. 相似文献
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《Microbiological research》2014,169(11):873-880
Regulation of gene expression is one of the mechanisms of virulence in pathogenic organisms. In this context, we would like to understand the gene regulation of acetamidase enzyme of Mycobacterium smegmatis, which is the first reported inducible enzyme in mycobacteria. The acetamidase is highly inducible and the expression of this enzyme is increased 100-fold when the substrate acetamide is added. The acetamidase structural gene (amiE) is found immediately downstream of three predicted open reading frames (ORFs). Three of these genes along with a divergently expressed ORF are predicted to form an operon and involved in the regulation of acetamidase enzyme. Here we report expression, purification and functional characterization of AmiA which is one of these predicted ORFs. Electrophoretic mobility shift assays showed that AmiA binds to the region between the amiA and amiD near the predicted promoter (P2). Over-expression of AmiA significantly lowered the expression of acetamidase compared to the wild type as demonstrated by qRT-PCR and SDS-PAGE. We conclude that AmiA binds near P2 promoter and acts as a repressor in the regulation of acetamidase operon. The described work is a further step forward toward broadening the knowledge on understanding of the complex gene regulatory mechanism of Mycobacterium sp. 相似文献
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