Summary Using an
Escherichia coli lac deletion strain lysogenized with lambda phage carrying a
metF-lacZ gene fusion (Flac), in which -galactosidase levels are dependent on
metF gene expression,
cis-acting mutations were isolated that affect regulation of the
Salmonella typhimurium metF gene. The mutations were located in a region previously defined as the
metF operator by its similarity to the
E. coli metF operator sequence. Regulation of the
metF gene was examined by measuring -galactosidase levels in
E. coli strains lysogenized with the wild-type Flac phage and mutant Flac phage. The results suggest that the mutations disrupt the methionine control system mediated by the
metJ gene product, but not the vitamin B
12 control system mediated by the
metH gene product. The results also demonstrate that negative control of the
metF gene by the
metH gene product and vitamin B
12 is dependent on a functional
metJ gene product.Abbreviations Ap
ampicillin
- dNTP
deoxyribonucleoside triphosphates
- GM
glucose minimal
- Km
kanamycin
- L-agar
Luria agar
- LM
lactose minimal
- SAM
s-adenosyl-
L-methionine
- TPEG
phenylethyl -
D-thiogalactoside
- X-gal
5-bromo-4-chloro-3-indolyl -
D-galactopyranoside
- []
designates plasmid-carrier state
- ::
novel joint
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