DNA POLYMERASE AND RNA POLYMERASE.pptx

DNA Polymerase And RNA Polymerase

1. TOPIC NAME : DNA POLYMERASE AND RNA POLYMERASE

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 β 1 and β 2 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.

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