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At least 235 records · Page 13Linked to original sources
PubMed1982

Meiosis in Coprinus: characterization and activities of two forms of DNA polymerase during meiotic stages.

Two forms of DNA polymerase have been studied in the basidiomycete Coprinus. DNA polymerase from basidiocarp tissues at zygotene-pachytene stage has been purified 3,500-fold and defined as DNA polymerase b by virtue of its insensitivity to N-ethylmaleimide and by its low molecular weight (76,000). This enzyme has optimal activity at pH 7.0 to 7.5, at 200 mM KCl, and at 25 degrees C incubation temperature. It can use polycytidylic acid-oligo(dG)12-18 as template primer in addition to homodeoxypolymers. The DNA polymerase a is mainly produced in the exponentially growing mycelium. It is sensitive to N-ethylmaleimide and has a temperature optimum at 35 degrees C. At the premeiotic S phase, activities from both polymerase a and polymerase b are found in cell-free extracts. The b enzyme is the only DNA polymerase produced during meiotic prophase. Its assayable activity exhibits two peaks, one at premeiotic S stage and one at pachytene. It is possible that DNA polymerase b is responsible for pachytene repairs involved in recombination.

DNA-Directed DNA Polymerase↗
PubMed1977

Effects on rat liver acetaldehyde dehydrogenases in vitro and in vivo by coprine, the disulfiram-like constituent of Coprinus atramentarius.

Coprine, the disulfiram-like constituent of the mushroom Coprinus atramentarius was found to inhibit the low-Km dehydrogenase in rat liver and to increase the acetaldehyde level in blood during ethanol metabolism in vivo. Coprine did not inhibit the low-Km enzyme in vitro, but the hydrolytic product of coprine, 1-aminocyclo-propanol, was a potent inhibitor both in vitro and in vivo. A rapid onset of inhibition was observed after administration of coprine and the inhibition was long-lasting. It is suggested that 1-aminocyclopropanol is responsible for the inhibition caused by coprine in vivo.

Acetaldehyde↗
PubMed2001

Kinetic stability of designed glycosylation mutants of Coprinus cinereus peroxidase.

The effect of glycans and surface mutations on protein unfolding induced by heat or urea has been studied. Removal of the only native high mannose type glycan in the N142P, N142T, and N142D CIP mutants reduced the lifetime to half of that of wtCIP at irreversible conditions of unfolding. The effect was moderate at reversible conditions. Five glycomutants designed to have 0, 1, 2, 4 and 6N glycans showed a correlation between increased carbohydrate mass and increased stability toward irreversible unfolding. The results are in agreement with a dampening effect of glycans on backbone fluctuation in both the native and the unfolded states. However, experiments in reversible conditions were less clear because of additional effects of an increasing number of amino acid substitutions and aggregation. Examples of strong effects from minor surface changes were also observed.

Binding Sites↗
PubMed1976

Genetic recombination of Coprinus. V. Repair synthesis of deoxyribonucleic acid and its relation to meiotic recombination.

Repair synthesis of DNA per se at pachytene is not needed for commitment to meiotic recombination although it is a necessary event to follow. Recombination frequency is governed by the rate of nicking and the time in which unrepaired nicks are allowed to match and crossover. Cold treatment at pachytene prevented repair synthesis, hence open nicks were accumulated to match and crossover, and a 3-fold increase in recombination resulted. The kinetics of cold temperature effect followed a quadratic function as shown by a computer simulation which agreed with our experimental data (Lu, 1974b). High temperature did not change the rate of repair synthesis. It did cause an increased nicking which led to a twofold increase in recombination and which entailed a higher rate of recovery repair synthesis.

Agaricales↗
PubMed1975

Growth and ultrastructural studies on the mitochondrial mutant of Coprinus lagopus.

The cytoplasmic acu-10 mutant of Corprinus lagopus has a respiratory deficiency due to an altered cytochrome component and is slower growing than wild type. When growth of wild type and acu-10 monokaryons and dikaryons were compared on solid medium and in liquid culture the mutation was found to restrict growth of the dikaryon more severely than that of the monokaryon. Ultrastructural studies revealed that faster growth of the acu-10 monokaryon occurred at the expense of maintaining the cytoplasmic cell contents and with little increase in the numbers of mitochondria. Cells of the acu-10 dikaryon were comparatively unvacuolated and contained greatly increased numbers of mitochondria. Mitochondria in cells of the mutant had a typical orthodox conformation with clear matrix and well defined cristae. In contrast, mitochondria in wild type cells had a more compact and elongated shape with dense matrix and less obvious cristae. The observed difference in mitochondrial ultrastructure is interpreted as one of conformation rather than structure and is attributed to impaired ability of mutant mitochondria to carry out oxidative phosphorylation. In an old cell of the mutant the mitochondria showed signs of recovering the wild type conformation.

Agaricales↗
PubMed1988

Transformation as a method of increasing gene copy number and gene expression in the basidiomycete fungus Coprinus cinereus.

Seven transformants having varying numbers of non-homologously integrated copies of the isocitrate lyase gene, acu-7, were analysed for enzyme activity. Maximum levels of activity, 3.8 times that of the wild type, were observed in a transformant with only two gene copies whereas eight gene copies in another transformant led to only 25% wild type activity. Acu+ transformants were not selected directly for expression of acu-7 but as cotransformants. Analysis of 14 transformants not expressing acu-7 showed that four contained transforming DNA sequences and significantly, two had evidence of non-homologously integrated tandem duplications of the entire acu-7 plasmid DNA. The site of integration of the gene was thus important in determining whether or not it was expressed and to what level it was expressed. A comparison of induced and uninduced levels of enzyme activity confirmed that the enzyme was still tightly regulated.

Agaricales↗
PubMed1999

Comparison of chitin content in the apical and distal parts of fungal hyphae in Basidiobolus ranarum, Neurospora crassa and Coprinus sterquilinus.

Primary cell wall is synthesized in the growth zone of hyphal apex in fungi and rigidified during maturation along the newly formed hypha. Cross-linking of cell-wall components and self-assembly of individual polysaccharide chains into microfibrils are supposed to be involved in the rigidification process. We determined the relative chitin content in the cell wall of hyphal tips and distal walls of three fungal species and demonstrated a general increase in relative chitin content in mature cell walls. Thus, this increase can be supposed to raise cell-wall rigidity as the principal role of chitin in the determination of cell-wall rigidity is beyond doubt.

Cell Wall↗
PubMed1979

Sugar transport in Coprinus cinereus.

Two transport systems for glucose were detected: a high affinity system with a Km of 27 muM, and a low affinity system with a Km of 3.3 mM. The high affinity system transported glucose, 2-deoxy-D-glucose (Km = 26 muM), 3-O-methylglucose (Km = 19 muM), D-glucosamine (Km = 652 muM), D-fructose (Km = 2.3 mM) and L-sorbose (Km = 2.2 mM). All sugars were accumulated against concentration gradients. The high affinity system was strongly or completely inhibited by N-ethylmaleimide, quercetin, 2,4-dinitrophenol and sodium azide. The system had a distinct pH optimum (7.4) and optimum temperature (45 degrees C). The low affinity system transported glucose, 2-deoxy-D-glucose (Km = 7.5 mM), and 3-O-methylglucose (Km = 1.5 mM). Accumulation again occurred against a concentration gradient. The low affinity system was inhibited by N-ethylmaleimide, quercetin and 2,4-dinitrophenol, but not by sodium azide. The rate of uptake by the low affinity system was constant over a wide temperature range (30--50 degrees C) and was not much affected by pH; but as the pH of the medium was altered from 4.5 to 8.9 a co-ordinated increase in affinity for 2-deoxy-D-glucose (from 52.1 mM to 0.3 mM) and decrease in maximum velocity (by a factor of five) occurred. Both uptake systems were present insporelings germinated in media containing sodium acetate as sole carbon source. Only the low affinity system could initially be demonstrated in glucose-grown tissue, although the high affinity system was restored by starvation inglucose-free medium. The half-ti me for restoration of high affinity activity was 3.5 min and the process was unaffected by cycloheximide. Addition of glucose to an acetate-grown culture inactivated the high affinity system with a half-life of 5--7.5 s. Addition of cycloheximide to an acetate-grown culture caused decay of the high affinity system with a half-life of 80 min. Regulation is thus thought to depend on modulation of protein activity rather than synthesis, and the kinetics of glucose, 2-deoxy-D-glucose and 3-O-methylglucose uptake would be consistent with there being a single carrier showing negative co-operativity. Analysis of transport defective mutants revealed defects in both transport systems although the mutants used were alleles of a single gene. It is concluded that this gene (the ftr cistron) is the structural gene for an allosteric molecule which serves both transport systems.

Agaricales↗
PubMed1977

Factors affecting the amount and the activity of the glutamate dehydrogenases of Coprinus cinereus.

Kinetic analyses done with cell-free extracts of this basidiomycete fungus showed that the NADP-linked glutamate dehydrogenase exhibited positively co-operative interactions with the substrates 2-oxoglutarate and NADPH, negatively co-operative kinetics with NADP+ and was extremely sensitive to inhibition of deamination activity by ammonium and/or ammonia. The NAD-linked enzyme showed positive co-operativity with NADH, Michaelis-Menten kinetics with all other substrates and was subject only to mild inhibitions by the reaction products. Considered together with the values of the Michaelis constants, these results indicate that the former enzyme is primarily concerned with the amination of 2-oxoglutarate when the concentration of this substrate exceeds about 4 mM, while the NAD-linked enzyme is able to aminate or deaminate as metabolic conditions require. Synthesis of both enzymes was repressed by addition of carbamyl phosphate or N-acetyl-glutamate to mycelial cultures growing in media containing glucose and ammonium as carbon and nitrogen sources. Growth in media containing urea results in repression of the NADP-linked glutamate dehydrogenase and derepression of the NAD-linked enzyme. Such results indicate a connexion between the glutamate dehydrogenases and the urea cycle. It is suggested that under normal conditions of growth on complex media nitrogen is assimilated in the form of amino acids and that the glutamate dehydrogenases act in support of transaminases to allow this process to continue, and in support of the urea cycle to allow the disposal of excess nitrogen.

Agaricales↗
PubMed2004

Promoter analysis of cgl2, a galectin encoding gene transcribed during fruiting body formation in Coprinopsis cinerea (Coprinus cinereus).

In the homobasidiomycete Coprinopsis cinerea, expression of the two fruiting body-specific galectins, CGL1 and CGL2, is controlled by nutrients, light and darkness and the A mating type genes. In this study, we analyzed the promoter of the cgl2 gene by measuring transcript levels by quantitative real-time PCR and show that regulation of CGL2 expression occurs at the transcriptional level. A minimal promoter sufficient to confer regulated expression of a heterologous reporter gene and comprising 627 base pairs from the start codon was defined. On the minimal promoter we identified a 120 bp sequence mediating induction of the cgl2 gene in constant darkness. Along with direct repeats (TGGAAG/TGGAAG/GGAA), the sequence contains a CRE consensus site (cAMP-responsive element, TGCGTCA) suggesting the involvement of cAMP signaling in cgl2 activation. No specific elements responsible for light repression and mating type regulation were found in the promoter.

Adaptation, Physiological↗
PubMed1997

Molecular analysis of the isocitrate lyase gene (acu-7) of the mushroom Coprinus cinereus.

The nucleotide sequence of the structural gene for isocitrate lyase (acu-7) is presented and features of its coding sequence and predicted protein are described. Several motifs were identified within the promoter region which are potentially involved in transcriptional regulation. Surprisingly, some of these occur within the coding sequence of an adjacent gene of unrelated function that terminates within 371 bp upstream from acu-7. The sequence of this second gene identified an N-acetylglucosamine-1-phosphate transferase.

Amino Acid Sequence↗