Characterization of Vacuolar Arginine Uptake and Amino Acid Efflux inNeurospora crassaUsing Cupric Ion to Permeabilize the Plasma Membrane

Noncircadian oscillations in amino acid transport have complementary profiles in assimilatory and foraging hyphae of Phanerochaete velutina

“…Under conditions of N demand, stored vacuolar amino acids are mobilized and there is growing biochemical and molecular evidence for the involvement of a specific set of tonoplast efflux transporters (Keenan & Weiss, 1997; Russnak et al ., 2001). Molecular insights into control of the switch between accumulation and release are also beginning to emerge, particularly from studies on selective permeabilization of the plasma membrane to allow direct access to the tonoplast (Keenan & Weiss, 1997; Roos et al ., 1997). While vacuolar amino acid uptake appears to be independent of the intravacuolar concentration, efflux is initiated immediately vacuolar amino acid levels exceed a threshold value (Keenan & Weiss, 1997; Roos et al ., 1997).…”

“…Molecular insights into control of the switch between accumulation and release are also beginning to emerge, particularly from studies on selective permeabilization of the plasma membrane to allow direct access to the tonoplast (Keenan & Weiss, 1997; Roos et al ., 1997). While vacuolar amino acid uptake appears to be independent of the intravacuolar concentration, efflux is initiated immediately vacuolar amino acid levels exceed a threshold value (Keenan & Weiss, 1997; Roos et al ., 1997). The consequences of such a system operating were explored in the simulation.…”

“…Because there is also extensive evidence that fungi accumulate amino acids in their vacuoles under conditions of high N-availability (Kitamoto et al, 1988;Watkinson, 1999), vacuolar transport was also included in the simulation. Although vacuolar uptake may be mediated by both high-affinity (Zerez et al, 1986) and low-affinity (Keenan & Weiss, 1997) tonoplast amino-acid transporters (Klionsky et al, 1990;Horák, 1997;Wipf et al, 2002), only a single saturable tonoplast transport system was included in the model. The kinetic parameters for the transporters and the constants used in the simulation are given in Fig.…”

A Highly Conserved Mechanism of Regulated Ribosome Stalling Mediated by Fungal Arginine Attenuator Peptides That Appears Independent of the Charging Status of Arginyl-tRNAs

“…The response to limitation appears mediated by the level of tRNA; the response to surplus appears to be mediated differently. Because fungi store large amounts of Arg in the vacuole (44) (the concentration of Arg in the vacuole of S. cerevisiae grown in Arg-containing medium is 430 mM (45) and a high concentration of Arg is also stored in the vacuole of N. crassa (46), it would seem logical that they possess a regulatory mechanism to modulate Arg biosynthesis in response to cytosolic concentrations of Arg far exceeding those necessary for the charging of tRNA.…”

In situ study of K+ transport into the vacuole of Saccharomyces cerevisiae

“…Also cells permeabilized with DEAE‐dextran (Huber‐Wälchli and Wiemken, 1979; Theuvenet et al , 1986) and cupric ions (Ohsumi et al , 1988) have been used. The latter have been extensive used mainly for the differential extraction of vacuolar and cytoplasmic contents (Keenan and Weiss, 1997). Techniques for plasma membrane permeabilization have been applied for diverse purposes as the in situ study of enzymatic activities or the purification of enzymes by using different treatments with detergents, such as cetyltrimethylammonium (Joshi et al , 1987) and digitonin (Gowda et al , 1988) or mechanical methods and freeze–thaw cycles (Oliveira et al , 1981).…”