Selection for Tn10 tet repressor binding to tet operator in Escherichia coli: isolation of temperature-sensitive mutants and combinatorial mutagenesis in the DNA binding motif.
We have constructed a genetic assay which selects positively for a functional interaction between Tet repressor and its cognate operator in Escherichia coli. In this strain Tet repressor blocks expression of lacI and lacZ. This leads to derepression of a lacPO controlled galK gene. The strain can be selected by growth on galactose as the sole carbon source and screened for the beta-galactosidase phenotype. These features allow the identification of one candidate among 10(8) false clones on a single plate. The assay was applied to select mutants with a ts DNA binding phenotype and to screen oligonucleotide generated Tet repressor mutants. Analysis of these mutations revealed that they affect DNA and inducer binding and possibly the dimerization domains. These mutations are located at residues 21, 48, 49, 89 and at the C terminus of the protein (193), respectively.
Wissmann
A
A
Lehrstuhl für Mikrobiologie, Friedrich Alexander Universität Erlangen/Nürnberg, Federal Republic of Germany.
Wray
L V
LV
Somaggio
U
U
Baumeister
R
R
Geissendörfer
M
M
Hillen
W
W
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000235:genetics*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009875:Operator Regions, Genetic; D010957:Plasmids; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D013696:Temperature
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D012097:Repressor Proteins; C034811:tetracycline resistance-encoding transposon repressor protein