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The function of the upstream region of the σ; 54 ‐dependent Klebsiella pneumoniae nifL promoter is sensitive to DNA supercoiling
Author(s) -
Whitehall Simon,
Austin Sara,
Dixon Ray
Publication year - 1993
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.1365-2958.1993.tb01240.x
Subject(s) - klebsiella pneumoniae , biology , dna supercoil , dna , upstream (networking) , function (biology) , plasmid , microbiology and biotechnology , genetics , escherichia coli , gene , dna replication , computer network , computer science
Summary The positive control protein NTRC activates transcription from the σ; 54 ‐dependent nifL and glnAp2 promoters of Klebsiella pneumoniae by binding to upstream enhancer‐like sequences and contacting downstream bound σ; 54 ‐RNA polymerase via looping of the intervening DNA. In contrast to the glnAp2 promoter, the activity of the nifL promoter is very sensitive to changes in DNA supercoiling both in vivo and in vitro. We have shown previously that the downstream elements of the nifL promoter are involved in the supercoiling response. In this study we find that the upstream region of nifL influences the supercoiling response of a hybrid nifL‐ginAp2 promoter both in vivo and in vitro , demonstrating that the nifL upstream region also confers supercoiling sensitivity. DNA supercoiling did not appear to influence binding of NTRC to its sites in the nifL upstream region, suggesting that another function of this region, most probably DNA loop formation, is sensitive to changes in DNA topology.