Energetics of vacuolar compartmentation of arginine in Neurospora crassa

Drainas, Constantin; Weiss, Richard L.

doi:10.1128/jb.150.2.770-778.1982

Cited by 19 publications

(8 citation statements)

References 20 publications

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“…siae and 25 to 40 mV for N. crassa (14, 68). The electrochemical potential is able to drive amino acid and ion transport (35,68,124) (Fig. 5).…”

Section: Functions Of Vacuole Acidificationmentioning

confidence: 99%

“…Although it has been well documented that amino acid uptake is an energy-requiring process (35,124,129,198), the means by which amino acids are retained against a concentration gradient are not as well understood. It has been proposed that polyphosphate serves as a cation trap and forms complexes that are involved in metabolite retention (38).…”

Section: Amino Acid Transport and Storagementioning

confidence: 99%

“…In fact, arginine is seen to accumulate in the vacuole during proline starvation. Inhibitors of glycolysis also lead to arginine mobilization (35), but, as is the case with glutamine and nitrogen starvation, the actual effector has not been identi-fied. The observation that respiratory inhibitors or uncouplers block vacuolar release of arginine (35) suggests an energy requirement for efflux.…”

Section: Amino Acid Transport and Storagementioning

confidence: 99%

See 2 more Smart Citations

The fungal vacuole: composition, function, and biogenesis.

Klionsky¹,

Herman²,

Emr³

1990

Microbiological Reviews

476

292

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“…siae and 25 to 40 mV for N. crassa (14, 68). The electrochemical potential is able to drive amino acid and ion transport (35,68,124) (Fig. 5).…”

Section: Functions Of Vacuole Acidificationmentioning

confidence: 99%

Section: Amino Acid Transport and Storagementioning

confidence: 99%

Section: Amino Acid Transport and Storagementioning

confidence: 99%

See 1 more Smart Citation

The fungal vacuole: composition, function, and biogenesis.

Klionsky¹,

Herman²,

Emr³

1990

Microbiological Reviews

476

292

View full text Add to dashboard Cite

“…The behavior of vacuolar arginine pools in living N. c(rassa mycelia is consistent with the energetics of vacuolar accumulation so far determined in vivo. Cells grown in minimal medium and labeled with [14C]arginine were treated with inhibitors of glycolysis, inhibitors or uncouplers of respiration, or both (74,75). Transport of cytosolic arginine into the vacuoles was blocked by inhibitors of respiration or uncouplers, which considerably lowered the energy charge.…”

Section: Arginine Transport By Vacuolesmentioning

confidence: 99%

Compartmental and regulatory mechanisms in the arginine pathways of Neurospora crassa and Saccharomyces cerevisiae.

Davis¹

1986

Microbiological Reviews

136

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Arginine metabolism has been studied intensively in manly organisms, beginning in earnest with the discovery of the urea cycle in mammals (139). The genetic control of the arginine pathway was the earliest example of the one-gene, one-enzyme relationship in the biochemical genetics of Neiurosporca crassa (206). The elucidation of the pathway in Escherichia coli followed soon thereafter, the term "repression'' having been coined to describe the regulatory behavior of acetylornithinase (229). The discovery of carbamoyl phosphate in 1955 (131) led to many comparative studies of its metabolism (52, 130, 152). A profound knowledge of arginine metabolism in N. crassa and Sacclhiaonvces (ceev'isiae has developed in the last 25 years. The subject justifies a comparative review, because the two organisms solve similar metabolic problems in different ways. It is likely that the fundamental phenomena of compartmentation and regulation in the two organisms can be seen throughout the evolutionary tree, used variously according to the demands of particular lifestyles. The synthesis of arginine in fungi has three main components: the synthesis of ornithine, the synthesis of carbamoyl phosphate, and the conversion of these two compounds to arginine. The catabolic pathway consists of the hydrolysis of arginine to ornithine and urea, the breakdown of urea to ammonia and carbon dioxide, and the conversion of ornithine to glutamate. A theme to be pursued is how the anabolic and catabolic pathways can each proceed to the exclusion of the other, given ornithine as a common intermediate. A related theme is how carbamoyl phosphate and ornithine are confined to the arginine pathway in the face of enzymes that might divert them to other fates. Both of these matters involve the compartmentation of small molecules by intracellular membranes, which in S. (ereiisiae is supplemented by elaborate enzyme regulatory mechanisms. This review describes the enzymology, genetics, and localization of the arginine enzymes of S. cere\eisiae and N. crassa. This is followed by descriptions of vacuolar function, enzyme regulation, and the integration of relevant factors in adaptation to different environments. Metabolic maps (Fig. 1 and 2) and a gene-enzyme directory (Table 1) are given for N. crassa(and S. cerevisiae. Arginine metabolism in these organisms has been reviewed in more limited ways previously (1

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“…Uptake of the radioactive arginine and its equilibrium with the vacuolar pool were complete within this period (9). Under these conditions there was no catabolism of arginine (4,9). Mycelia were then harvested by filtration on Whatman no.…”

Section: Downloaded Frommentioning

confidence: 92%

Energy requirement for the mobilization of vacuolar arginine in Neurospora crassa

Drainas¹,

Weiss²

1982

J Bacteriol

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The bulk of the intracellular arginine pool in exponentially growing mycelia of Neurospora crassa is sequestered in the vacuoles. Vacuolar arginine effluxes from the vacuoles into the cytosol and is catabolized to ornithine and urea upon nitrogen starvation. The energy requirement for mobilization has been studied by treating nitrogen-starved mycelia with inhibitors of respiration or glycolysis or an uncoupler of respiration. Mobilization was inhibited by the inhibitors or the uncoupler of respiration, but not by the inhibitors ofglycolysis. The inhibitors and the uncoupler of respiration reduced the ATP pool and the energy charge of the treated mycelia. The inhibitors of glycolysis reduced the ATP pool but had no effect on the energy charge. The results indicate that mobilization of arginine from the vacuoles requires metabolic energy. The forms of this energy and the mode of its associations with the mobilization process are discussed.Nutritional stresses stimulate a variety of metabolic processes which do not occur in organisms under normal growth conditions. In fungi, nitrogen starvation results in the expression of a number of metabolic systems which utilize alternative sources of nitrogen-containing metabolites. These systems include a variety of pathways leading to the production of ammonia (5) and transport systems for nitrogen-containing metabolites (7). All of these systems are repressed or impaired when the fungi are growing on a preferred nitrogen source such as ammonia. This phenomenon is called nitrogen metabolite control (7).One example of a nitrogen metabolite-regulated system is the catabolism of vacuolar arginine in response to nitrogen starvation in Neurospora crassa. Mycelia of this ascomycete have a large intracellular arginine pool. The bulk of this pool, >98%, is sequestered in the vacuoles (9,11). When mycelia are deprived of nitrogen, vacuolar arginine effluxes across the tonoplast into the cytosol, where it is catabolized as an alternative source of nitrogen. This phenomenon has been termed mobilization of vacuolar arginine (5). The mechanism of translocation of arginine across the tonoplast is not clear. It is not known whether this translocation involves an active transport mechanism regulated by nitrogen metabolite control or a facilitated exchange in which some metabolite(s) replaces or displaces arginine from the vacuole. There are indications that the level of intracellular glutamine might be involved in the mobilization of the vacuolar arginine (T. L. Legerton and R. L. Weiss, manuscript in preparation); glutamine appears to be the effector for the control of a number of nitrogen metabolite-regulated systems (7). This report deals with the energy requirement for mobilization. The effect of various energy inhibitors on mobilization of vacuolar arginine has been examined. Inhibitors of oxidative phosphorylation have been shown to inhibit mobilization. The data support the hypothesis that energy is necessary for the proper functioning of the mechanism that mobilizes vacuolar arginine...

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Energetics of vacuolar compartmentation of arginine in Neurospora crassa

Cited by 19 publications

References 20 publications

The fungal vacuole: composition, function, and biogenesis.

The fungal vacuole: composition, function, and biogenesis.

Compartmental and regulatory mechanisms in the arginine pathways of Neurospora crassa and Saccharomyces cerevisiae.

Energy requirement for the mobilization of vacuolar arginine in Neurospora crassa

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