SUMMARY: Arginine and methionine transport by mycelium was investigated.

A single uptake system is responsible for the transport of arginine, lysine and ornithine. Transport is energy-dependent and specific for these basic amino acids. The value for arginine is 1 x 10 M, and is 2.8 nmol/mg dry wt/min; for lysine is 8 x 10 M; for lysine as inhibitor of arginine uptake is 12 μM, and for ornithine is 3 mM.

On minimal medium, methionine is transported with a of 0.1 mM and about 1 nmol/mg dry wt/min; transport is inhibited by azide. Neutral amino acids such as serine, phenylalanine and leucine are probably transported by the same system, as indicated by their inhibition of methionine uptake and the existence of a mutant specifically impaired in their transport.

The recessive mutant , unable to transport neutral amino acids, was isolated as resistant to selenomethionine and -fluorophenylanine. This mutant has unchanged transport of methionine by general and specific sulphur-regulated permeases.


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