Properties of a Basic Amino Acid Permease in Neurospora crassa

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.

Section: Methodsmentioning

confidence: 99%

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

DeBusk¹,

Ogilvie²

1984

“…Before growth on any of these compounds can occur, they must first be transported into the cells. A number of studies (5,15,19,21,22,25) have revealed in Neurospora the presence of at least four distinct amino acid transport systems specific for (i) L-neutral amino acids, (ii) L-basic amino acids, (iii) acidic amino acids, and (iv) a "general" system for both D-and L-neutral and basic amino acids. A system apparently specific for L-methionine has also been reported (16).…”

mentioning

confidence: 99%

“…At various time intervals portions were removed and the reaction was terminated by freezing. The samples were stored frozen, until analyzed by spotting 5-gliter samples on thin-layer plates (Eastman chromatogram sheet, cellulose with fluorescent indicator) which had been hand scored to 19 individual channels, 1 cm wide by 20 cm long. The samples were then chromatographed with ethanol: acetic acid: water (65:1:34) solvent for 160 to 180 *min.…”

mentioning

confidence: 99%

Peptide Utilization by Amino Acid Auxotrophs of Neurospora crassa

Wolfinbarger

Marzluf

1974

The ability of auxotrophs of Neurospora crassa to grow on certain tripeptides, despite the presence of excess competing amino acids, suggests it has an oligopeptide transport system. In general, dipeptides did not support growth except in those instances where extracellular hydrolysis occurred, or where the dipeptide appeared to be accumulated by an uptake system which is sensitive to inhibition by free amino acids. Considerable intracellular peptidase activity toward a large number of peptides was demonstrated, including a number of peptides which could not be utilized for growth. The intracellular peptidase activity was shown to be selective for amino acid composition and sequence (N-terminal or C-terminal) within the peptide; glycine-containing peptides were particularly poor substrates for peptidase activity. Only a small amount of extracellular peptidase activity could be detected.

“…Mutations which cause an alteration in basic amino acid transport specificity include bat (18), hlp-l (3), and strain CR-10 which is resistant to the arginine analogue canavanine (13). In addition to the permeases with charge specificity, a general amino acid transport system with very broad substrate specificity has been described in Neurospora and found to be present under certain conditions (10).…”

mentioning

confidence: 99%

Histidine Uptake in Strains of Neurospora crassa with Normal and Mutant Transport Systems

Magill,

Sweeney,

Woodward

1972

Kinetic parameters for three systems of active histidine uptake by germinated conidia of Neurospora crassa have been measured. Each system appears to follow typical Michaelis-Menten kinetics when studied separately from the other systems. Under the conditions studied, the general amino acid transport system was found to account for the major portion of histidine uptake from low concentrations. Three types of transport mutants with altered growth inhibition patterns were selected in a histidine auxotroph. Growth of one mutant, type basa, could be inhibited by the addition of methionine to a histidine-supplemented medium, and another type, neua, could be inhibited by the addition of arginine. These mutants were shown to be lacking active histidine uptake by the basic amino acid and neutral amino acid transport systems, respectively. Another type of double mutant (his-3, neur) could be inhibited only by the addition of very high concentrations of methionine in the presence of arginine and histidine, and the mutation appeared to have altered the specificity of the neutral amino acid permease.on August 1, 2020 by guest