Position effect on expression of dsd genes cloned onto multicopy plasmids.
In the D-serine deaminase system of Escherichia coli, which is regulated by positive control, we have fouand a complete lack of trans activation in vivo with multicopy dsd hybrid plasmids. A PLASmid carrying the regulatory gene, dsdC+, did not promote expression of chromosomal dsdCO+A+ loci, nor did a chromosomal dsdC+ gene promote expression of plasmid-borne dsdC delta O+A+ (dsd regulatory gene negative) restriction fragments. However, hybrid plasmids that comprise the entire dsd system (dsdC+O+A+) are highly inducible for the enzyme. These dsd hybrid plasmid deoxyribonucleic acids functioned well as templates in the in vitro coupled transcription-translation system. In vitro-synthesized dsdC+ protein promoted expression of the dsdA+ operation efficiently. Exogenously purified dsdC+ protein also activated expression of several dsdC delta O+A+ plasmid deoxyribonucleic acid templates in vitro. An explanation that reconciles these results with previous dominance studies is presented.
D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005809:Genes, Regulator; D012695:L-Serine Dehydratase / Q000096:biosynthesis / Q000235:genetics*; D009876:Operon; D010957:Plasmids
D012695:L-Serine Dehydratase