title: Mechanism of autonomous control of the Escherichia coli F plasmid: different complexes of the initiator/repressor protein are bound to its operator and to an F plasmid replication origin.
abstract: E protein, the 29 kd product of the F plasmid repE gene, plays both positive and negative roles in the autoregulation of F replication. We have cloned and expressed the repE gene in an inducible ATG-fusion vector and have detected specific binding of E protein to the repE operator and to four 19-base pair direct repeats (incB) within the F plasmid replication origin ori2. Binding of E protein at the repE operator occurs with higher affinity than at ori2(incB) and gives almost complete protection to at least 30 base pairs, whereas binding of E protein to the direct repeats in the ori2 region shows an alternating pattern of enhanced and reduced sensitivity to DNAase cleavage consistent with a protein-induced folding of the DNA. These results provide direct biochemical support for a model of F plasmid replication in which the E protein serves both as an initiator of replication and as an autorepressor of its own synthesis.
mesh_terms: D001483:Base Sequence; D003090:Coliphages / Q000235:genetics; D004261:DNA Replication; D004262:DNA Restriction Enzymes; D004279:DNA, Viral / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics*; D005144:F Factor; D009876:Operon; D010448:Peptide Initiation Factors / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D004279:DNA, Viral; D010448:Peptide Initiation Factors; D012097:Repressor Proteins; D014157:Transcription Factors; D004262:DNA Restriction Enzymes