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161.
Ethanol-sensitive mutants of Saccharomyces cerevisiae 总被引:3,自引:0,他引:3
Saccharomyces cerevisiae mutants unable to grow at ethanol concentrations at which the wild type strain S288C does grow, have been isolated. Some of them show additional phenotypic alterations in colony size, temperature sensitivity and viability in ethanol, which cosegregate with the growth sensitivity in ethanol. 21 selected monogenic ethanol-sensitive mutants define 20 complementation groups, denominated ETA1 to ETA20, which indicates that there is a high number of genes involved in the ethanol tolerance/sensitivity mechanism.Out of 21 selected monogenic mutants, 20 are not altered in the glycolytic pathway since, when maintained in glucosesupplemented medium, they can produce as much ethanol as the wild type and at about the same velocity. Nor do any of the mutants seem to be altered in the lipid biosynthetic pathway since, whether grown in the absence or in the presence of ethanol, their concentration of fatty acids and ergosterol is similar to that of the wild type under the same conditions. Therefore growth sensitivity to ethanol does not seem necessarily to be related to carbohydrate or lipid metabolism.Non-common abbreviations YP
yeast extract peptone medium
- YPD
yeast extract peptone dextrose agar or medium
- YPG
yeast extract peptone glycerol agar
- YPDE
yeast extract peptone dextrose ethanol agar or medium
- SD
yeast nitrogen base dextrose agar
- SPO
yeast extract potassium acetate glucose agar
- PD
parental ditype
- NPD
non-parental ditype
- TT
tetratype 相似文献
162.
Looking for probes of gated channels: studies of the inhibition of glucose and choline transport in erythrocytes 总被引:2,自引:0,他引:2
Two seemingly contradictory sets of observations have been made in studies of biological transport, which are essential for our understanding of the transport mechanism: carriers are integral membrane proteins, which span the membrane and are not free to rotate across the membrane; carriers appear to function like a ferryboat, with a substrate binding site moving back and forth from one side of the membrane to the other. To reconcile these facts, it is necessary to postulated gated channels connecting the substrate site with the two membrane surfaces: the channels are arranged so that as one opens the other closes, with the result that the substrate site is alternately accessible from opposite sides of the membrane. Based on these properties, the following distinguishing features of molecules specifically bound in the channels may be predicted: if sufficiently bulky, they inhibit transport; they bind outside the substrate site (though adjacent to it), they bind asymmetrically either to the outward-facing carrier and on the outer surface of the membrane, or to the inward-facing carrier and on the inner surface of the membrane. The asymmetrical inhibition of the glucose and choline transport systems of erythrocytes by various inhibitors is examined, and the behavior in every case is found to conform with these criteria. From the results it may be concluded that the glucose carrier binds cytochalasin B in the inner gated channel and phloretin and tetrathionate in the outer gated channel.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
163.
Clathrin-associated proteins contain bound nucleotide 总被引:2,自引:0,他引:2
An alcohol dehydrogenase isolated from Zymomonas mobilis was found to be activated by ferrous ions but not by zinc, after inactivation with metal-complexing agents. Cobaltous ions also re-activated to a lesser extent. It is suggested that in this species the alcohol dehydrogenase naturally contains iron. Kinetic studies on the iron-treated enzyme indicate an 'alcohol activation' phenomenon, which may have physiological relevance in overcoming product inhibition during fermentation. 相似文献
164.
I T Toledo e Souza B L Wajchenberg F Prestes Cesar J S Almeida Neto 《Hormones et métabolisme》1983,15(12):575-580
Insulin and C-peptide (free insulin and C-peptide in insulin-treated patients) were measured after glucose stimulation in nine Type II diabetics on chlorpropamide, eleven insulin-treated maturity-onset diabetics and in 8 normal controls. Dissociation between C-peptide and insulin response to glucose was observed in several diabetics. The relation between incremental molar areas under C-peptide and insulin curves, after glucose challenge (delta CPR - delta IRI/delta CPR) were used to evaluate the hepatic insulin extraction in all but the insulin-treated diabetics. The lower insulin requirements and better control of the short-duration insulin-treated maturity-onset diabetics in relation to the long-term ones could not be explained either by the residual insulin secretion or by the level of "insulin antibodies". The chlorpropamide-responsive patients presented higher insulin levels after the glucose challenge and a lower hepatic insulin extraction than the non-responsive ones. 相似文献
165.
Electro-optical measurements on aqueous suspension of purple membrane from Halobacterium halobium 总被引:5,自引:5,他引:0 下载免费PDF全文
The permanent dipole moment, polarizability, and the retinal angle of Halobacterium halobium purple membranes were determined at different pH values. All of the parameters have a maximum between pH 5 and 6. There is a reversal in the direction of the permanent dipole moment near pH 5. The value of permanent dipole moment was determined to be 60 D/protein at pH 6.6, and the value obtained for polarizability was 3 X 10(-28) Fm2/membrane fragment. The retinal angle of all-trans retinal was 0.8 degrees smaller than that of the 13-cis conformation. 相似文献
166.
Intestinal brush border vesicles of a Mediterranean sea fish (Dicentrarchus labrax) were prepared using the Ca2+-sedimentation method. The transport of glucose, glycine and 2-aminoisobutyric acid is energized by an Na+ gradient (). In addition, amino acid uptake requires Cl? in the extravesicular medium (2-aminoisobutyric acid more than glycine). This Na+- and Cl?-dependent uptake is electrogenic, since it can be stimulated by negative charges inside the vesicles. The specific Cl? requirement of glycine and 2-aminoisobutyric acid transport is markedly influenced by pH, a change from 6.5 to 8.4 reducing the role played by Cl?. In the presence of Cl?, the of 2-aminoisobutyric acid uptake is reduced and its is enhanced. Cl? affects also a non-saturable Na+-dependent component of this amino acid uptake. Amino acid transport is also increased by intravesicular Cl? (2-aminoisobutyric acid less than glycine). This effect is more concerned with glucose uptake, which can be then multiplied by 2.3. A concentration gradient () as well as the presence of Na+ in the incubation medium seems to enter into this requirement. This intravesicular Cl? effect is not influenced by pH between 6.5 and 8.4. 相似文献
167.
The Na+ channel activity (tetrodotoxin sensitive 22Na+ flux induced by veratridine and/or anemone toxin II) was studied in two fractions of brain cell plasma membranes, named A and B, isolated by the method of Gray and Whittaker ((1962) J. Anat. 96, 79–87) from rats 5, 10, 30 and 60 days old. The 22Na+ flux was measured in membrane vesicles formed by the isolated membranes, in the absence of drugs (control), in the presence of veratridine, and in the presence of veratridine plus tetrodotoxin. Fraction A consists primarily of neuronal and glial membranes in rats of 5 and 10 days of age, while in the older rats this fraction becomes enriched in myelin. In Fraction A of 5-day-old and 10-day-old rats, veratridine (25 μM) increases the 22Na+ flux 2.4- and 1.6-fold, respectively, and the increment continues to diminish with age, until it becomes negligible in the 60-day-old rats. Fraction B consists of synaptosomes and membrane vesicles, and at the four ages studied veratridine (25 μM) causes an increment of the 22Na+ flux of about 2.5-fold. Fractions A and B from 10-day-old rats, and Fraction B from 60-day-old rats, which are sensitive to veratridine, also respond to anemone toxin II. When veratridine is used in presence of anemone toxin II (0.5 μM), the for veratridine is diminished and the maximum 22Na+ flux is increased. The increments of 22Na+ flux caused by veratridine and/or anemone toxin II in Fractions A and B are blocked by tetrodotoxin ( approx. 5 nM). Fraction A from 60-day-old rats could be subfractionated by osmotic shock and sucrose gradient centrifugation to obtain three subfractions, two of which are enriched in axolemma and display Na+ chennel activity. The other subfraction is enriched in myelin and shows no Na+ channel actiivty. The plasma membrane preparations from young rats (up to 10 days) are devoid of myelin and are useful for studies of Na+ channel activity. 相似文献
168.
Selection of Wine Yeasts for Growth and Fermentation in the Presence of Ethanol and Sucrose 总被引:5,自引:3,他引:2 下载免费PDF全文
Tahía Benítez Lucas del Castillo Andrs Aguilera Jaime Conde E. Cerdolmedo 《Applied microbiology》1983,45(5):1429-1436
To optimize the conversion of carbohydrates to ethanol, strains of several Saccharomyces species were examined for the ability to grow and ferment in a range of sucrose and ethanol concentrations. A total of 632 wine yeasts, most of them isolated from wineries in Andalusia and Extremadura, southwestern Spain, were subjected to screening and selection. Growth and fermentative capacity in different ethanol and sucrose concentrations varied from one strain to another. There was no correlation between growth and fermentative capacity. The best 35 strains grew in 15% ethanol and fermented in 18% ethanol. Ethanol accumulated, although at a reduced rate, after the cells stopped growing. Most yeast strains were highly fermentative in 50% sucrose. Some of them effectively utilized the carbohydrates of the culture, yielding final ethanol concentrations of > 14%. Of the 35 selected strains, 16 were promising for genetic analysis and breeding because of their capacity to sporulate. These strains were homothallic, and their spores were viable. The meiotic products analyzed so far were also homothallic. 相似文献
169.
The specific activity of bisphosphoglycerate synthase (EC 2.7.5.4) is significantly higher in rat mature erythrocytes than in reticulocytes from phenylhydrazine treated animals, while 2,3-bisphosphoglycerate levels do not differ between them. The enzyme specific activity and the concentration of 2,3-bisphosphoglycerate are both negligible in the erythroid cell pool from the bone marrow of anaemic animals. Thus, a cellular specialization in the last stages of erythropoiesis is confirmed. Human bisphosphoglycerate synthase shows a lower specific activity than that of rat without a parallel decrease in 2,3-bisphosphoglycerate levels. 相似文献
170.
Regulation of lipogenesis in vivo by glucose availability and insulin secretion in maternal and foetal tissues during late gestation in the rat. Effect of glucose intubation, streptozotocin-induced diabetes and starvation. 总被引:1,自引:1,他引:0 下载免费PDF全文
Administration of an oral load of glucose did not change the rate of lipogenesis in maternal liver during late gestation. However, streptozotocin-induced diabetes or starvation decreased maternal liver lipogenesis at 20-22 days of gestation. Glucose intubation, on the other hand, increased foetal lipogenesis at 21-22 days. In addition, maternal starvation decreased foetal lipogenesis and plasma insulin concentration. However, chronic hyperglycaemia induced by streptozotocin administration to the mother did not change foetal liver lipogenesis. 相似文献