title: The F plasmid ccd autorepressor is a complex of CcdA and CcdB proteins.
abstract: The ccd operon of plasmid F produces three proteins, CcdA, CcdB, and RepD. Prior research has established that the operon is autorepressed and that at least CcdB, but not RepD, is required for autorepression. A role for CcdA in autorepression was suggested but not clearly shown. We now present a series of biochemical experiments which show that both CcdA and CcdB proteins are required for maximal formation of protein-ccd operator complexes. We also show that CcdA and CcdB are present in a complex whether or not ccd operator is present. The clear implication is that autorepressor is a complex of CcdA and CcdB. We also map the start site of the ccd transcript thus providing the first experimental evidence for the location of the ccd promoter.
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic/Foundation, Rochester, MN 55905.
authors.forename: J E
authors.initials: JE
authors.lastname: Tam
authors.forename: B C
authors.initials: BC
authors.lastname: Kline
mesh_terms: D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D003850:Deoxyribonuclease I / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005144:F Factor; D008969:Molecular Sequence Data; D009875:Operator Regions, Genetic; D009876:Operon; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins / Q000302:isolation & purification / Q000378:metabolism*; D015183:Restriction Mapping; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; D003850:Deoxyribonuclease I