PubMed Health⌕ Search

Biomedical subjects

M Piotrowska

Publications and source records attributed to M Piotrowska.

At least 19 recordsLinked to original sources
PubMed2001

The Aspergillus nidulans metE gene is regulated by a second system independent from sulphur metabolite repression.

Mutations in the Aspergillus nidulans metE gene lead to requirement for O-acetylhomoserine. The gene was cloned by complementation of the metE31 mutation. The coding sequence was found to be interrupted by two introns of 66 and 50 bp, respectively. metE codes for a peptide of 489 amino acids which belongs to the family of homoserine O-acetyltransferases and a well-defined superfamily of alpha/beta hydrolases. Transcription of the metE gene is strongly up-regulated by a severe limitation of methionine, but not of cysteine. This gene is the first sulphur metabolism gene described in A. nidulans which is not regulated by the sulphur metabolite repression system in which cysteine acts as the low-molecular-weight effector.

Amino Acid Sequence↗
PubMed2000

sconC, a gene involved in the regulation of sulphur metabolism in Aspergillus nidulans, belongs to the SKP1 gene family.

sconC, which encodes a negative regulator of sulphur metabolism in Aspergillus nidulans was cloned, sequenced, and found to belong to the highly conserved family of SKP1 genes essential for many cell functions, including cell cycle regulation. The ORF of 722 bp, encoding a protein of 161 amino acids, is interrupted by four introns. There is a fifth intron (135 bp long) in the upstream untranslated sequence. Two point mutations in conserved regions were identified in the mutant alleles sconC3 and sconC1, which result in relief of sulphur metabolite repression. The SCONC protein contains the PEST sequence common for proteins that are subject to rapid turnover. Transformation of the sconC3 mutant with sconB+ restores the wild-type phenotype. The sconB gene encodes a protein containing the F-box, a domain known to interact with Skp1 proteins. By analogy with other systems, it seems likely that the SCONC protein interacts with SCONB. sconC mRNA is present in the sconC3 and sconB2 mutants and the level of the sconC transcript seems not to be significantly regulated by supplementation of the medium with sulphur.

Amino Acid Sequence↗
PubMed1998

The Aspergillus nidulans sulphur regulatory gene sconB encodes a protein with WD40 repeats and an F-box.

The Aspergillus nidulans gene sconB, one of the four identified genes controlling sulphur metabolite repression, was cloned and analysed. It encodes a polypeptide of 678 amino acids containing seven WD repeats characteristic of the large WD40 family of eukaryotic regulatory proteins. The SCONB protein has nuclear localisation signals and is very similar to the Neurospora crassa SCON2 and Saccharomyces cerevisiae Met30 proteins, both of which are involved in the regulation of sulphur metabolism. The N. crassa scon-2 gene complements the sconB2 mutation. All three proteins also contain a newly identified motif, the F-box, found in a number of eukaryotic regulatory proteins. This motif is responsible, at least in some cases, for ubiquitin-mediated proteolysis. The sconB transcript is derepressed under sulphur limitation conditions and partly repressed by high methionine.

Amino Acid Sequence↗
PubMed1996

Transfer of cadmium, lead, and zinc from industrially contaminated soil to crop plants: a field study.

The documeneed adverse health effects of soil Cd and Pb have led to public concern over soil contamination with metals. A 4-year field experiment was conducted to study the transfer of Cd, Pb, and Zn from soil contaminated by smelter flue-dust to crop plants grown in a rotation. The soil was amended with Pb?Zn smelter flue-dust (2-66.8 kg per 10 m(2) plot) to simulate the long-term effect that the smelting of non-ferrous metal ore has on arable soils. The treated soil became strongly contaminated with metals (Cd 3.2-106 mg/kg, Pb 146-3452 mg/kg, Zn 465-11 375 mg/kg). Concentrations of Cd, Pb, and Zn in barley grain, barley straw meadow bluegrass, red clover, and potatoes were generally low. The highest metal concentrations were found in potato tubers (intact), meadow bluegrass, and barley straw. The observed reduction in crop yield was probably the result of possible nutrient imbalances rather than of metal (Zn, Cu) phytotoxicities. Zn and Cd uptake by the plants can be described by the saturation (plateau) model (y = ax(b), b < 1). The relationship between Pb in the soil and plants was linear with an extremely low slope (0.0001-0.0003). No excessive dietary intake of Cd is expected when Cd concentrations in barley grain and potato tubers grown on the contaminated soil are not higher than 0.6 and 1.0 mg/kg, respectively. Based on the risk analysis and taking into account the saturation model of the soil-plant metal relationship, it was concluded that, under the conditions of this experiment (neutral soil pH), soil with Cd concentrations of up to 30 mg/kg is still safe for production of these crop plants.

Journal Article↗
PubMed1995

[Mercury in muscle tissue of flounder Platychthis flesus from two sites in the Gulf of Gdansk].

Total mercury concentration was determined in the muscle tissue of flounder collected under Stegna (ca. 1 mile east of the Vistula River outlet) and under Gdynia (ca. 12 miles northwest of the Vistula River Outlet) sampling sites in the Gulf of Gdańsk in 1992 and 1993. The method of measurement was cold-vapour atomic absorption spectrometry (CV-AAS) after wet digestion of the samples with concentrated nitric acid. The arithmetic means of mercury concentration in muscle tissue of flounder collected under Stegna were 46 +/- 24 in 1992 and 57 +/- 47 in 1993, while for those under Gdynia 20 +/- 19 and 26 +/- 18, micrograms/kg on a wet weight basis, respectively. Mercury concentrations in muscle tissue of flounder collected under Stegna were positively correlated with the body length and body weight of fish (0.05 < p < 0.001), while in the case of specimens collected under Gdynia no such relationships were found. These observations seem to imply that Vistula River is an important source and pathway of mercury entrance into the Gulf of Gdańsk.

Animals↗
PubMed1993

Candida valida--a yeast lacking the reverse transsulphuration pathway.

A new yeast strain PGR-13 was classified as the variant of Candida valida. It is unique in its ability to ferment well and ready formation of respiratory deficient mutants. The lack of the reverse transsulphuration pathway was found to be a common trait of both PGR-13 and the type strain of Pichia membranaefaciens.

Candida↗
PubMed1990

A yeast with unusual sulphur amino acid metabolism.

A yeast strain highly resistant to propargylglycine (an inhibitor of cystathionine gamma-lyase) was isolated from air. It was partially characterized, but it has not been identified with any known yeast species. Its sulphur amino acid metabolism differed from that of other fungi by the lack of the reverse transsulphuration pathway from methionine to cysteine, as no activity of cystathionine beta-synthase or cystathionine gamma-lyase was found. The functional lack of this pathway was confirmed by growth tests and by experiments with [35S]methionine. In contrast to Saccharomyces cerevisiae neither homocysteine synthase nor the sulphate assimilation pathway were repressible by methionine in the new strain; on the contrary, a regulatory effect of cysteine was observed.

Alkynes↗
PubMed1980

Effect of regulatory mutations of sulphur metabolism on the levels of cysteine- and homocysteine-synthesizing enzymes in Neurospora crassa.

1. Regulation of four enzymes involved in cysteine and homocysteine synthesis, i.e. cysteine synthase (EC 4.2.99.8), homocysteine synthase (EC 4.1.99.10), cystathionine beta-synthase (EC 2.1.22) and gamma-cystathionase (EC 4.4.1.1) was studied in the wild type and sulphur regulatory mutants of Neurospora crassa. 2. Homocysteine synthase and cystathionine beta-synthase were found to be regulatory enzymes but only the former is under control of the cys-3 - scon system regulating several enzymes of sulphur metabolism, including gamma-cystathionase. 3. The results obtained with the mutants strongly suggest that homocysteine synthase plays a physiological role as an enzyme of the alternative pathway of methionine synthesis. Cysteine synthase activity was similar in all strains examined irrespective of growth conditions. 4. The sconc strain with derepressed enzymes of sulphur metabolism showed an increased pool of sulphur amino acids, except for methionine. Particularly characteristic for this pool is a high content of hypotaurine, a product of cysteine catabolism.

Carbon-Oxygen Lyases↗
PubMed1978

Catabolite repression in Aspergillus nidulans; the role of glutamine synthetase.

A mutant (nit8) with a lowered activity of glutamine synthetase (GS) was isolated in Aspergillus nidulans. The levels of GS and of an arginine catabolic enzyme, ornithine transaminase (OTA) were assayed under a variety of growth conditions leading to repression, depression and induction of OTA in the wild type, nit8 and several regulatory mutants. The results obtained appear to exclude the possibility of involvement of GS in the regulation of arginine catabolism in A. nidulans.

Arginine↗
PubMed1976

Basic and neutral amino acid transport in Aspergillus nidulans.

Arginine and methionine transport by Aspergillus nidulans mycelium was investigated. A single uptake system is responsible for the transport of arginine, lysine and ornithine. Transport is energy-dependent and specific for these basic amino acids. The Km value for arginine is 1 X 10(-5) M, and Vmax is 2-8 nmol/mg dry wt/min; Km for lysine is 8 X 10(-6) M; Kt for lysine as inhibitor of arginine uptake is 12 muM, and Ki for ornithine is mM. On minimal medium, methionine is transported with a Km of 0-I mM and Vmax about I nmol/mg dry wt/min; transport is inhibited by azide. Neutral amnio acids such as serine, phenylalanine and leucine are probably transported by the same system, as indicated by their inhibition of methionine uptake and the existence of a mutant specifically impaired in their transport. The recessive mutant nap3, unable to transport neutral amino acids, was isolated as resistant to selenomethionine and p-fluorophenylanine. This mutant has unchanged transport of methionine by general and specific sulphur-regulated permeases.

Amino Acids↗