Physiological and regulatory properties of the general amino acid transport system of Neurospora crassa

DeBusk, R M; DeBusk, A. G.

doi:10.1128/jb.143.1.188-197.1980

Cited by 31 publications

(22 citation statements)

References 26 publications

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“…Another possible mechanism of pFPA resistance may be based on alterations in permease functions. Mutations at the pmg locus of N. crassa -obtained by selecting for pFPA resistancedisrupt the function of the general amino acid transport system, called system II [31,32]. The Neurospora pmg gene was isolated and characterized [33]: the sequence exhibited high degrees of similarity to Inda 1, a presumptive permease gene of T. harzianum induced by growth on cell walls of R. solani [34].…”

Section: Discussionmentioning

confidence: 99%

Isolation and characterization of protease overproducing mutants of Trichoderma harzianum

Szekeres

Kredics

Zsuzsanna

et al. 2004

FEMS Microbiology Letters

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Several Trichoderma strains have been reported to be effective in controlling plant diseases, and the action of fungal hydrolytic enzymes is considered as the main mechanism involved in the antagonistic process. Strain Trichoderma harzianum T334 is a potential biocontrol agent against plant pathogenic fungi with the ability to produce low levels of proteases constitutively. To improve its fungal antagonistic capacity, mutagenetic program was undertaken for the construction of protease overproducing derivates. The mutant strains were obtained by means of UV-irradiation and were selected for p-fluorophenyl-alanine resistance or altered colony morphology. It was revealed by means of specific chromogenic protease substrates that both trypsin-like and chymotrypsin-like protease secretion was elevated in most of the mutant strains. The profiles of isoenzymes were different between the mutants and the wild-type strain, when examined by gel filtration chromatography. Certain mutants proved to be better antagonists against plant pathogens in in vitro antagonism experiments. This study suggests the possibility of using mutants with improved constitutive extracellular protease secretion against plant pathogenic fungi.

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Section: Discussionmentioning

confidence: 99%

Isolation and characterization of protease overproducing mutants of Trichoderma harzianum

Szekeres

Kredics

Zsuzsanna

et al. 2004

FEMS Microbiology Letters

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“…Strains were maintained on solidified 1 x Vogel medium N (36) containing NH4NO3 as the nitrogen source, 2% sucrose as the carbon source, and 1.5% agar. The culture storage and growth regimens are described by DeBusk and DeBusk (7). Isolation of the pmn; pmb; pmg; lox strain.…”

Section: Methodsmentioning

confidence: 99%

“…The conversion of amino acid to keto acid was measured by using a microassay in which dialyzed culture medium was incubated with radiolabeled phenylalanine, and the keto acid product was detected. The assay is a modification of that of Woodward and Cirillo (7,39). To determine whether an amino acid could potentially serve as a substrate for deaminase action, the test amino acid was added at 100 times the concentration of the radiolabeled phenylalanine, and the ability to interfere with phenylpyruvate production was measured.…”

Section: Methodsmentioning

confidence: 99%

“…In the filamentous fungus Neurospora crassa, transport is accomplished by three constitutive amino acid permeases and three specialized permeases. The constitutive permeases include a neutral amino acid-specific (N) system, a basic amino acid-specific (B) system, and a general (G) system that can transport all classes of amino acid (5,7,18,20,22,23,37). Three additional systems that function during advanced stages of development have been proposed for the transport of the imino acid proline, of acidic amino acids, and of the sulfurcontaining amino acid methionine during sulfur limitation (10,24,25,38,40).…”

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Participation of an extracellular deaminase in amino acid utilization by Neurospora crassa

DeBusk¹,

Ogilvie²

1984

J Bacteriol

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A strain of Neurospora crassa defective in amino acid transport can utilize a variety of amino acids for growth when readily metabolizable nitrogen is limiting. Growth is accompanied by the production of an extracellular deaminase that converts the amino acid to its respective keto acid plus equimolar quantities of utilizable nitrogen in the ammonium ion form. Production of the deaminase is subject to ammonium repression. The relationship between the ability of an amino acid to trigger deaminase production and the presence of particular amino acid permease deficiencies is complex. Four classes of amino acids have been defined with respect to this relationship. The existence of multiple extracellular deaminases is discussed.

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“…Each of these strains is available from the authors. All strains were maintained in lx Vogel medium N supplemented with 2% sucrose and solidified with 1.5% agar as previously described (2,13).Amino acid transport assays. For the conidial assays, cells were incubated at 25°C (0.1 mg of dry weight per ml of incubation medium, final concentration) in lx Vogel medium N in which the NH4NO3 had been replaced with equimolar KNO3.…”

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confidence: 99%

Characterization of 2-aminoisobutyric acid transport in Neurospora crassa: a general amino acid permease-specific substrate

Ogilvie-Villa¹,

DeBusk²,

DeBusk³

1981

J Bacteriol

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We report the characterization of an amino acid permease-specific substrate for Neurospora crassa. The neutral amino acid 2-aminoisobutyric acid was transported solely by the general amino acid permease and not by the neutral amino acid permease. Furthernore, this substrate was not metabolized after transport. The potential for a system-specific nonmetabolizable substrate as a tool in the analysis of amino acid transport and its regulation is discussed.Several laboratories have been involved with the analysis of amino acid transport in the fungus Neurospora crassa. The early goals of this research were to determine the number and types of systems which were responsible for transporting amino acids. This approach defined the strategy for amino acid transport by N. crassa as involving a limited number of constitutive permeases which transport families of structurally related amino acids: a neutral (N) system which is specific for neutral aliphatic or aromatic amino acids, a basic (B) system which transports positively charged amino acids, and a general (G) system which handles all classes of amino acids (1, 2, 4-7, 9-11, 14).Each family of amino acids is, therefore, transported both by the family-specific system and by the G system. Such overlap in substrate specificity between systems has made it difficult to ascribe particular properties to single systems. One approach to this problem involves the construction of mutant strains defective for the activity of one or more transport systems so that only the system of interest remains active. This approach has been very useful in defining the number of transport systems that exist and the physiological and kinetic properties of each. A second approach involves the identification and use of a system-specific amino acid substrate to monitor the activity of the permease of interest without eliminating the activities of the other perneases. This approach allows one to detect interactions among functional systems, an advantage not possible with the mutant approach. In addition, a permease-specific substrate is a useful tool, in combination with the mutant approach, for molecular studies of the components which comprise a particular transport system.We describe here the transport of the amino acid 2-aminoisobutyric acid (AIB) and its properties as a general amino acid permease-specific substrate. MATERLS AND METHODSStrains and growth of cultures. The wild-type strain 74a (FGSC 988) was obtained from the Fungal The pmn, pmb, and pmg strains are defective for the neutral amino acid-specific permease, the basic amino acid-specific permease, and the general amino acid permease, respectively, and are isogenic with the wild type. Each of these strains is available from the authors. All strains were maintained in lx Vogel medium N supplemented with 2% sucrose and solidified with 1.5% agar as previously described (2,13).Amino acid transport assays. For the conidial assays, cells were incubated at 25°C (0.1 mg of dry weight per ml of incubation medium, final concentration) in lx Vog...

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Physiological and regulatory properties of the general amino acid transport system of Neurospora crassa

Cited by 31 publications

References 26 publications

Isolation and characterization of protease overproducing mutants of Trichoderma harzianum

Isolation and characterization of protease overproducing mutants of Trichoderma harzianum

Participation of an extracellular deaminase in amino acid utilization by Neurospora crassa

Characterization of 2-aminoisobutyric acid transport in Neurospora crassa: a general amino acid permease-specific substrate

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