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Sigma factor

Subunit of bacterial RNA polymerase that recognizes the promoter and initiates transcription.

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Sigma factor

Subunit of bacterial RNA polymerase that recognizes the promoter and initiates transcription.

It is a subunit that transiently associates with the core of bacterial RNA polymerase and gives it specificity to recognize promoter sequences.

It is indispensable for the initiation of transcription in bacteria: without it, RNA polymerase cannot locate the correct starting site of a gene. Several alternative sigma factors allow the cell to activate different sets of genes depending on conditions.

The video states that, together with RNA polymerase, it binds a promoter characterized by the −35 box and the −10 box or Pribnow box, forming a closed complex that then opens, and that it is released after about 10 nucleotides have been synthesized, leaving the enzymatic core to continue elongation.

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