vidence for Involvement of Escherichia coliGenes pmbA, csrAand a Previously Unrecognized Gene tldD, in the Control of DNA Gyrase by letD( ccdB) of Sex Factor F

• Published in: Journal of molecular biology Vol. 256; no. 3; pp. 483 - 502
• Main Authors: Murayama, Nobuhiro, Shimizu, Hiroki, Takiguchi, Souichi, Baba, Yoshifumi, Amino, Hisako, Horiuchi, Tadao, Sekimizu, Kazuhisa, Miki, Takeyoshi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1996
• Subjects: Escherichia coli; F plasmid; letD( ccdB) gene; DNA gyrase; chromosome segregation; Escherichia coli; F plasmid; letD( ccdB) gene; DNA gyrase; chromosome segregation
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1006/jmbi.1996.0103

The
letA(
ccdA) and
letD(
ccdB) genes of the F plasmid, located just outside the sequence essential for replication, contribute to stable maintenance of the plasmid in
Escherichia colicells. The
letDgene product acts to inhibit partitioning of chromosomal DNA and cell division by inhibiting DNA gyrase activity, whereas the
letAgene product acts to reverse the inhibitory activity of the
letDgene product. To identify the host factor(s) involved in this process, we analyzed the mutants that escaped
letDexpression and their suppressor, and found that the three
E. coligenes
tldD,
tldEand
zfiAparticipate in the process, in addition to the
groEgenes we reported previously. The
tldDand
tldEmutations made cells tolerant for
letDexpression, as did
groESmutations, while the mutation in the
zfiAgene made
tldD,
tldEand
groESmutants LetD sensitive. We hypothesize that these gene products are factors that modulate activity of DNA gyrase along with the
letDgene product; the
zfiAgene product acts to inhibit interaction between the LetD protein and the A subunit of DNA gyrase, while the
tldD,
tldEand
groEgene products act to suppress the inhibitory activity of the
zfiAgene product. The
tldD,
tldE, and
zfiAgenes are located at 70.4, 96.0 and 58.2 minutes on the
E. colichromosome, respectively, and code for proteins with relative molecular masses of 51,000, 48,000 and 6800, respectively.
tldDis a novel gene, but the
tldEand
zfiAgenes proved to be the
pmbAgene (production of Microcin B17) and the
csrAgene (carbon storage regulator), respectively.