what is the function of the sigma subunit (factor) of E.coli RNA polymerase in transcription.

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DNA dependent RNA polymerase is the main enzyme involved in gene expression and regulation.A functional RNA polymerase has a core composition of 2 alpha subunit 1 beta 1 beta' and one Omega subunits which along with the Sigma factor forms the RNA polymerase holoenzyme.These all , together are involved in transcription initiation, elongation and termination. Core enzyme is proficient enough to carry out elongation but cannot initiate transcription from promoter on its own. Sigma factor comes into play here,its forms a holoenzyme which recognises and initiates transcription. Sigma factor binds to -35 and -10 consensus promoter elements.At later stages Sigma factor is also involved in abortive RNA synthesis and promoter escape. It is homlogous to eukaryotic transcription factor TFIIB. Number of Sigma factor varies between bacterial species. There are 7 Sigma factors in case of e coli. Structurally they have four main conserved domains.

gladiator answered 1 year ago

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