Affiliation:
1. Department of Biology, Emory University, Atlanta, Georgia 30322
Abstract
ABSTRACT
ppGpp regulates gene expression in a variety of bacteria and in plants. We proposed previously that ppGpp or its precursor, pppGpp [referred to collectively as (p)ppGpp], or both might regulate the activity of the enzyme polynucleotide phosphorylase in
Streptomyces
species. We have examined the effects of (p)ppGpp on the polymerization and phosphorolysis activities of PNPase from
Streptomyces coelicolor
,
Streptomyces antibioticus
, and
Escherichia coli
. We have shown that (p)ppGpp inhibits the activities of both
Streptomyces
PNPases but not the
E. coli
enzyme. The inhibition kinetics for polymerization using the
Streptomyces
enzymes are of the mixed noncompetitive type, suggesting that (p)ppGpp binds to a region other than the active site of the enzyme. ppGpp also inhibited the phosphorolysis of a model RNA substrate derived from the
rpsO-pnp
operon of
S. coelicolor
. We have shown further that the chemical stability of mRNA increases during the stationary phase in
S. coelicolor
and that induction of a plasmid-borne copy of
relA
in a
relA
-null mutant increases the chemical stability of bulk mRNA as well. We speculate that the observed inhibition
in vitro
may reflect a role of ppGpp in the regulation of antibiotic production
in vivo
.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
37 articles.
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