sigma factor


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Related to sigma factor: RNA polymerase, TATA box

sig·ma fac·tor

a factor that inhibits the nonspecific DNA binding of RNA polymerase, as well as helping to identify the starting point of transcription; it promotes attachment of the RNA polymerase to specific initiation sites.
Synonym(s): σ factor

sigma factor

n.
A protein component of bacterial RNA polymerase that recognizes the correct site on DNA for initiating transcription of a gene and that is usually released soon after transcription begins.

sigma factor

a subunit of RNA polymerase that determines the site where transcription begins. The sigma factor confers PROMOTER specificity, assisting the RNA polymerase in recognising the correct promoter sequence on the DNA to initiate transcription. In ESCHERICHIA COLI the principal sigma factor is σ70, the housekeeping factor (see HOUSEKEEPING GENES).There are alternative sigma factors governing the expression of genes in response to different environmental conditions; for example σ38, the STATIONARY PHASE factor, and σ32, the heat shock factor (see HEAT SHOCK PROTEIN). These factors can associate with the RNA polymerase, displacing σ70 and directing the enzyme to initiate transcription from other promoters. see ANTISIGMA FACTOR.
References in periodicals archive ?
36] Garrett ES, Perlegas D, Wozniak DJ Negative control of flagellum synthesis in Pseudomonas aeruginosa is modulated by the alternative sigma factor AlgT (AlgU).
The first, and most notable, is a putative RNA polymerase sigma factor (CDS pCT_066) within the sequence, which shares homology with genes found in only 4 closely related plasmids (pO26vir; pO113, TP113, and pSERB1) and has limited identity to homologue SigB in Yersinia frederiksenii.
The bacteria's defenses are controlled by an alternative sigma factor, a protein that acts as a switch for certain genes.
New topics and sections address biosensors, bio-control, bottled water, Enterobacter sakazakii, food sanitizers, milk, probiotics, proteobacteria, quorum sensing, and sigma factors.