Pleiotropic Deficiency in Nitrogen‐Uptake Systems and Derepression of Nitrogen‐Catabolic Enzymes in npr‐1 Mutants of Saccharomyces cerevisiae

Abstract

The npr‐I mutation has two types of effects in Saccharomyces cerevisiae. On one hand, several nitrogen‐catabolic enzymes are derepressed in the presence of ammonia, glutamine, or asparagine, which provoke their repression in a wild‐type strain. On the other hand, the activity of several ammonia‐sensitive permeases is decreased (from 50–100% depending on the permease considered) in npr‐1 cells, independently of the nitrogen source used for growth. Our results favour the idea that the primary effect of the npr‐l mutation is on the permeases, and that the derepression of the enzymes is a consequence of the reduced uptake rate of the repressing nitrogen compounds. Hence, the product of the npr‐I gene appears to be directly involved in the development of the activity of a set of permeases which transport nitrogen compounds and which are regulated by nitrogen effectors. Copyright © 1982, Wiley Blackwell. All rights reserved