Gene roles in the prn cluster of Aspergillus nidulans.

The roles of the four genes of the prn gene cluster involved in L-proline catabolism in Aspergillus nidulans have been investigated. prnD and prnC encode, respectively, proline exidase and Δ(I)-pyrroline-5-carboxylate (P5C) dehydrogenase. prnB is almost certainly the structural gene for the proline-inducible major proline permease. The prnA product has no structural role in these activities but is a positive acting regulatory molecule necessary for the expression of prnD, prnC and, to a lesser extent, prnB. Evidence favouring de novo synthesis of P5C dehydrogenase upon induction in the presence of a functional prnA allele is also presented.