title: Pleiotropic deficiency in nitrogen-uptake systems and derepression of nitrogen-catabolic enzymes in npr-1 mutants of Saccharomyces cerevisiae.
abstract: The npr-1 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-1 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-1 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.
mesh_terms: D026905:Amino Acid Transport Systems; D026922:Amino Acid Transport Systems, Acidic; D000641:Ammonia / Q000378:metabolism; D001216:Asparagine / Q000378:metabolism; D019731:Carbon-Nitrogen Ligases; D005786:Gene Expression Regulation; D005973:Glutamine / Q000378:metabolism; D008025:Ligases / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D026905:Amino Acid Transport Systems; D026922:Amino Acid Transport Systems, Acidic; C503357:DIP5 protein, S cerevisiae; D026901:Membrane Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D005973:Glutamine; D001216:Asparagine; D000641:Ammonia; D008025:Ligases; D019731:Carbon-Nitrogen Ligases; C023270:urea carboxylase (hydrolyzing); D009584:Nitrogen