Nimetu
The core enzyme has 5 subunits (~400 kDa):
· 2: the two subunits assemble the enzyme and recognize regulatory
factors. Each subunit has two domains: CTD (C-Terminal domain) binds
the UP element of the extended promoter, and NTD (N-terminal domain)
binds the rest of the polymerase.
· : this has the polymerase activity (catalyzes the synthesis of RNA) which
includes chain initiation and elongation.
· ': binds to DNA (nonspecifically).
· : restores denatured RNA polymerase to its functional form in vitro. It has
been observed to offer a protective/chaperone function to the ' subunit in
Mycobacterium smegmatis. Now known to promote assembly.
In order to bind promoter-specific regions, the core enzyme requires another
subunit, sigma (). The sigma factor greatly reduces the affinity of RNAP for
nonspecific DNA while increasing specificity for certain promoter regions,
depending on the sigma factor
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