Affiliation:
1. Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw 12, Poland
Abstract
Secondary mutants able to utilize
d
-histidine,
dhu
, were isolated in histidine auxotrophs of
Salmonella typhimurium
. Mutations of one class (
dhuA
) are closely linked with the
hisP
locus which codes for a component of histidine permease. The specific activity of
l
-histidine permeation was estimated as increased two- to seven-fold in
dhuA
mutants. The
dhuB
mutants which have not been mapped also had elevated specific activity of
l
-histidine permeation. The uptake of
d
-histidine, barely detectable in the parental strains, was prominent in
dhuA
mutants and showed an apparent Michaelis constant about 1,000-fold higher than that observed with
l
-histidine. No change was detected in the kinetics of
l
-histidine permeation.
d
- and
l
-histidine competed in the uptake process. Tertiary mutants which lost the ability to grow on
d
-histidine were isolated by ampicillin counter-selection in
dhuA his
−
strains. All of them mapped in the
dhuA hisP
region. Most of them had all known properties of
hisP
mutants. It is inferred from these data that the
dhuA
mutations increase synthesis of components critical to
d
- and
l
-histidine permeation.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference11 articles.
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4. Histidine and aromatic permeases of Salmonella typhimurium;Ames G. F.;J. Bacteriol.,1968
5. Glutamate transport in wild-type and mutant strains of Escherichia coli;Halpern Y. S.;J. Bacteriol.,1965
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