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Transcription and autoregulation of the stabilizing functions of broad‐host‐range plasmid RK2 in Escherichia coli, Agrobacterium tumefaciens and Pseudomonas aeruginosa
Author(s) -
Davis Tamara L.,
Helinski Donald R.,
Roberts Richard C.
Publication year - 1992
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1992.tb01371.x
Subject(s) - biology , operon , agrobacterium tumefaciens , plasmid , genetics , repressor , promoter , escherichia coli , agrobacterium , inverted repeat , gene , transcription (linguistics) , microbiology and biotechnology , transformation (genetics) , transcription factor , gene expression , genome , linguistics , philosophy
Summary The broad‐host‐range plasmid RK2 has been shown to encode several proteins important for its maintenance within bacterial populations of a number of Gram‐negative bacteria. Their genes are organized into two operons: parCBA and parD. These operons have been proposed to be transcribed from two divergent promoters, p‐parCBA and p‐parD , located within a sequence of approximately 150 bases. In this report we identify and characterize the sequences required for regulated transcription from these promoters in Escherichia coli, Agrobacterium tumefaciens and Pseudomonas aeruginosa. Both of these promoters are repressed by their own gene products in the same manner in all three bacteria tested, with ParA functioning as the primary repressor of p‐parCBA and ParD functioning as the repressor of p‐parD. The binding regions of these proteins were determined through deletion analyses, DNA mobility shift assays, and an examination of the effect of mutations in this region. Based on these observations, the ParA protein appears to bind to either two inverted repeat or two direct repeat sequences, one downstream from the transcriptional initiation site and the other upstream of the p‐parCBA ‐35 box. The ParD protein appears to bind to one inverted repeat sequence, located between the ‐35 and ‐10 boxes of p‐parD.