sigma factor activity
Sigma factors act as the promoter specificity subunit of eubacterial and plant plastid multisubunit RNA polymerases, whose core subunit composition is often described as alpha(2)-beta-beta-prime. Although sigma does not bind DNA on its own, when combined with the core to form the holoenzyme, the sigma factor binds specifically to promoter elements. The sigma subunit is released once elongation begins.
GO:0003700
DNA-binding transcription factor activity
is_a
DNA-dependent RNA polymerase promoter selection factor
exact
bacterial sigma factor activity
narrow
core DNA-dependent RNA polymerase binding promoter specificity activity
exact
plastid sigma factor activity
narrow
promoter selection factor activity
narrow
sigma transcription factor
exact