RNA Polymerase

1
RNA Polymerase

• Subunits a ß and ß

2
RNA Polymerase

• An enzyme that catalyzes the formation of an RNA
  polynucleotide strand using the base sequence of
  a DNA molecule as a template
• No primer is required to initiate synthesis

3
RNA Polymerase from E. Coli

• The holoenzyme is composed of 5 subunits a (2),
  ß, ß, s
• Molecular Weight 500,000 Da

4
a subunit

• Required for assembly of the enzyme
• Interacts with some regulatory proteins
• Also involved in catalysis of RNA
• 2 Domains
• aCTD (C-Terminal Domain) binds to the UP element
  (located upstream from the -35 region increases
  transcription) of the promoter.
• aNTD (N-Terminal Domain) binds to the rest of
  the polymerase.

5
ß subunit

• coded by the rpoB gene.
• Main subunit involved in catalysis of RNA
• Responsible for chain initiation and elongation

6
ß subunit

• binds to the DNA template
• - Composed of three residues that combine with
  the ß subunit to create a claw-like clamp that
  attaches to the DNA template
• Nonspecific
• - until the holoenzyme has the s subunit, it
  cannot locate the promoter accurately

7
ß subunit continued

• Nonspecific
• - The promoter region is found by binding and
  disassociating until the holoenzyme reaches the
  promoter region