Effects of structural changes in the dsdA-dsdC intergenic region on D-serine deaminase synthesis.
Single-base-pair changes well upstream of its transcription initiation site resulted in partially to fully constitutive expression of the D-serine deaminase structural gene, dsdA, independently of the cyclic AMP-cyclic AMP-binding protein complex and of the specific D-serine deaminase activator protein. These promoter mutations appear to define a consensus sequence that is repeated several times. Basal expression of dsdA+ was also strongly enhanced by subcloning on multicopy plasmids, by the DNA gyrase inhibitor novobiocin, and in dsdC(Con) mutants by increasing growth temperature. These results suggest that activation of dsdA+ expression by the dsdC-encoded protein involves distortion of promoter DNA. A dsdA translation start at bp -731 was verified by subcloning of dsdC+. Plasmid-specified activator at a high concentration interfered with chromosomal dsdC(Con) expression, and the interference was enhanced by deletion of most of the intergenic region from the plasmid. Even at a high concentration, however, plasmid-specified activator did not activate expression of chromosomal dsdA+, and in one case it was actually repressive. These results confirm the strong cis tropism of plasmid-specified dsdC-encoded protein and suggest that it is mediated by multiple sites in the dsdA-dsdC intergenic region.
McFall
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E
Department of Microbiology, New York University School of Medicine, New York 10016.
Nikam
S S
SS
Palchaudhuri
S
S
D001483:Base Sequence; D003001:Cloning, Molecular; D016384:Consensus Sequence; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D007438:Introns; D007544:Isopropyl Thiogalactoside / Q000494:pharmacology; D012695:L-Serine Dehydratase / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D009675:Novobiocin / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D012694:Serine / Q000494:pharmacology; D013696:Temperature; D014158:Transcription, Genetic
D009675:Novobiocin; D007544:Isopropyl Thiogalactoside; D012694:Serine; D012695:L-Serine Dehydratase