Transport of L-Glutamine by Neurospora

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 m and V max were determined for glutamine transport by both systems. The glutamine analogues methionine sulphoximine and γ-glutamyl hydroxamate appear to be transported by the same permeases that transport glutamine. In addition to determining the physiological properties of glutamine transport, we examined whether the pmn;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.