Regulation of the trfA and trfB promoters of broad host range plasmid RK2: identification of sequences essential for regulation by trfB/korA/korD.

AUTOR(ES)

Theophilus, B D

RESUMO

Using a plasmid containing a transcriptional fusion in which the E.coli galK gene is expressed from the trfB promoter of broad host range plasmid RK2 we show that transcription from the trfB promoter is repressed by the products of both the trfB and korB genes as we have previously predicted from the sequence homology of the trfA and trfB promoters and the fact that the trfA promoter is regulated by trfB and korB. These loci, trfB and korB are normally transcribed from the trfB promoter. Thus the trfB incC korB operon of RK2 is doubly autogeneously regulated. In addition, we describe the isolation and characterization of a mutant trfA promoter which has become insensitive to repression by trfB as a result of a point mutation within the inverted repeat sequence previously predicted to be the trfB protein binding site. These results provide strong evidence for our previously proposed model for control of transcription from the trfA and trfB promoters.

Documentos Relacionados

• The trfB region of broad host range plasmid RK2: the nucleotide sequence reveals incC and key regulatory gene trfB/korA/korD as overlapping genes.
• The trfA and trfB promoter regions of broad host range plasmid RK2 share common potential regulatory sequences.
• The korB gene of broad host range plasmid RK2 is a major copy number control element which may act together with trfB by limiting trfA expression.
• Broad-host-range properties of plasmid RK2: importance of overlapping genes encoding the plasmid replication initiation protein TrfA.
• Replication of the broad-host-range plasmid RK2: direct measurement of intracellular concentrations of the essential TrfA replication proteins and their effect on plasmid copy number.