DNA polymerase is an enzyme that reads existing DNA strands as templates and creates two new strands through phosphodiester bond formation. It was first discovered in E. coli by Arthur Kornberg. DNA polymerase has a structure resembling an open right hand with palm, finger, and thumb domains that each perform different functions in nucleotide recognition and binding. RNA polymerase is a multi-subunit enzyme responsible for copying DNA sequences into RNA during transcription from 5' to 3'. It contains alpha, beta, and sigma subunits that play various roles in binding to promoter regions and catalytic activity.
2. DNA POLYMERASE
• DNA polymerase are group of enzymes reads existing DNA strands as template
and create two new strand by the formation of phospho-di-ester bond.
• The DNA dependent DNA polymerase was first discovered by Arthur Kornberg
from E.Coli bacteria, so that he got nobel prize in 1959. Therefore DNA
polymerase are considered as Kornberg Enzyme.
3. STRUCTURE OF DNA POLYMERASE
The DNA polymerase made up of sub-domains looks like an open right hand as
palm, fingers and thumb. Each of them have different function.
•The palm contains the catalytic active sites.
• The fingers help in recognition of nucleotide and
binding.
•The thumb is for binding DNA substrate.
There is domain between thumb and finger known
as pocket, which is made up of two regions. i.e
Insertion region and post-insertion region.
4. FUNCTION OF DNA POLYMERASE
• The main function of DNA polymerase is the addition of nucleotide or
polymerization activity to the 3’ end of the existing DNA strand.
• DNA polymerase also have exonuclease function. There are two exonuclease
domain.
3’ → 5’ exonulcease domain involved in mismatched repair mechanism.
5’ → 3’ exonuclease domain displaced primer and also mutated segment of
DNA during DNA repair mechanism.
• It also involved in replication fidelity.
5. RNA POLYMERASE
• RNA polymerase is a multi-subunit enzyme that is responsible for copying DNA
sequence into a RNA sequence during the transcription process in the direction
of 5’-3’.
STRUCTURE OF RNA POLYMERASE
• Two identical α subunits involved in the molecular communication and binds to
the promoter region of the DNA strand.
• Two similar but not identical β1 and β2 play a major role in catalytic activity.
• No function found till date of the small “ω” subunit.
• A sigma subunit bind to the core-enzyme to form
a holoenzyme, that contains two zinc molecules
or a zinc and one magnesium ion.
