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The Bacillus subtilis sigma(X) protein is an extracytoplasmic function sigma factor contributing to survival at high temperature
Author(s) -
Xuejun Huang,
Amy L. Decatur,
Alexeï Sorokin,
John Helmann
Publication year - 1997
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.179.9.2915-2921.1997
Subject(s) - sigma factor , biology , bacillus subtilis , sigma , gene , mutant , genetics , transcription (linguistics) , subfamily , promoter , transcription factor , rpos , microbiology and biotechnology , gene expression , bacteria , linguistics , physics , philosophy , quantum mechanics
The sigX gene, identified as part of the international effort to sequence the Bacillus subtilis genome, has been proposed to encode an alternative sigma factor of the extracytoplasmic function (ECF) subfamily. The sigX gene is cotranscribed with a downstream gene, ypuN, during logarithmic and early stationary phases of growth. We now report that strains lacking sigma(X) are impaired in the ability to survive at high temperature whereas a ypuN mutant has increased thermotolerance. We overproduced and purified sigma(X) from Escherichia coli and demonstrate that in vitro, both sigma(A) and sigma(X) holoenzymes recognize promoter elements within the sigX-ypuN control region. However, they have distinct salt optima such that sigma(A)-dependent transcription predominates at low salt while sigma(X)-dependent transcription predominates at high salt. A 54-bp region upstream of sigX suffices as a sigma(X)-dependent promoter in vivo, demonstrating that sigX is at least partially under positive autoregulatory control. Mutation of ypuN increases expression from the sigma(X)-dependent promoter in vivo, suggesting that ypuN may encode a negative regulator of sigma(X) activity.

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