Specificity and regulation of peptide transport on Neurospora crassa.

The tripeptide, glycyl-d,l-leucyl-l-tyrosine was chemically synthesized in radioactive form and used to directly study the specificity, regulation, and properties of an oligopeptide transport system in Neurospora. Transport activity is sensitive to azide but does not result in the accumulation of the intact peptide; rather, the radioactive label is accumulated as free tyrosine. Inhibition studies suggest that the transport system probably has a relatively wide range of specificity and is responsible for uptake of short oligopeptides of quite distinct sequences. However, free amino acids and dipeptides are not transported significantly, if at all, by the oligopeptide transport system. A free amino group appears to be a requirement for peptide transport. A mutant strain that is unable to use various peptides for growth is further described and shown to be reduced greater than 90% in transport of the tripeptide.