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J. Bacteriol., 10 1995, 5434-5439, Vol 177, No. 19
MR Rondon, R Kazmierczak and JC Escalante-Semerena
Transcription of the cob/pdu regulon of Salmonella typhimurium is activated
by the PocR regulatory protein in response to 1,2-propanediol (1,2-PDL) in
the environment. Nutritional analysis and DNA sequencing confirmed that a
strain defective in expression of the cob/pdu regulon in response to
1,2-PDL lacked a functional gshA gene. gshA encodes gamma-glutamylcysteine
synthetase (L-glutamate:L-cysteine gamma-ligase [ADP forming]; EC 6.3.2.2),
the enzyme that catalyzes the first step in the synthesis of glutathione
(GSH). The DNA sequence of gshA was partially determined, and the location
of gshA in the chromosome was established by two-factor crosses. P22
cotransduction of gshA with nearby markers showed 21% linkage to srl and 1%
linkage to hyd; srl was 9% cotransducible with hyd. In light of these data,
the gene order gshA srl hyd is suggested. The level of reduced thiols in
the gshA strain was 87% lower than the levels measured in the wild-type
strain in both aerobically and anaerobically grown cells. 1,2-PDL-dependent
transcription of cob/pdu was studied by using M. Casadaban's Mu-lacZ
fusions. In aerobically grown cells, transcription of a cbi-lacZ fusion
(the cbi genes are the subset of cob genes that encode functions needed for
the synthesis of the corrin ring) was 4-fold lower and transcription of a
pdu-lacZ fusion was 10-fold lower in a gshA mutant than in the wild-type
strain. Expression of the cob/pdu regulon in response to 1,2-PDL was
restored when GSH was included in the medium.(ABSTRACT TRUNCATED AT 250
WORDS)
Copyright © 1995, American Society for Microbiology
Glutathione is required for maximal transcription of the cobalamin biosynthetic and 1,2-propanediol utilization (cob/pdu) regulon and for the catabolism of ethanolamine, 1,2-propanediol, and propionate in Salmonella typhimurium LT2
Department of Bacteriology, University of Wisconsin--Madison 53706- 1567, USA.
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