Transport of L-Glutamine by Neurospora

Abstract

The transport of the neutral amino acid L-glutamine by Neurospora crassa occurred by means of two permeases : the neutral-specific permease and the general permease. For both transport systems, accumulation of L-glutamine was a saturable process that occurred against a concentration gradient and was dependent upon metabolic energy, suggesting that accumulation is a carrier-mediated active transport process. The transported glutamine was incorporated into cellular protein. The kinetic values K , and V,,, were determined for glutamine transport by both systems. The glutamine analogues methionine sulphoximine and yglutamyl hydroxamate appear to be transported by the same permeases that transport glu tamine.In addition to determining the physiological properties of glutamine transport, we examined whether thepmn;pmb;pmg;nit-2 strain could transport this amino acid. This strain is defective for constitutive amino acid transport and for the ability to utilize amino acids as sole nitrogen sources, with the exception of glutamine. No glutamine transport was detected, suggesting that glutamine utilization by this strain is not due to its ability to transport this amino acid.

The Negative Transcriptional Regulator NmrA Discriminates between Oxidized and Reduced Dinucleotides

“…In vivo post-translational modulation of NIT2 activity has been implicated, as in vitro the nmr1-encoded N-terminally deleted forms of NMR1 protein bind directly to the zinc finger region and the extreme C-terminal 30 amino acids of NIT2 (15)(16)(17). The interactions were demonstrated in a qualitative manner by using the yeast two-hybrid system, as well as steady state techniques that included electrophoretic mobility shift assay and column binding using His 6 -and glutathione S-transferasetagged fragments of the NIT2 protein as a bait.…”

Microbial Enzymes and Biotechnology

“…Thus mutations of nmr-l allow production of these enzymes in the presence of glutamine, NHt or glutamate (Debusk & Ogilvie, 1984a). Growth on NHt, glutamine or glutamate represses a large number of enzymes acting on nitrogenous substrates.…”

“…Growth on NHt, glutamine or glutamate represses a large number of enzymes acting on nitrogenous substrates. Its expression requires inducer (one of many amino acids), lifting of nitrogen source repression and the presence of the nit-2 gene product (Debusk & Ogilvie, 1984b). These compounds repress the formation of the nit-2 gene product which acts as a positive control agent for use of poor nitrogen sources.…”