Question

The prokaryotic DNA polymerase V has several novel features particularly well-suited for its role in bypassing certain kinds of DNA lesions such a bulky adducts or intercalators. These features have both costs and benefits to the cell. Explain the positive and/or negative effects of the following features:

a) lack of processivity compared to DNA polymerase III

b) ability to accommodate bulky adducts in the active site of the enzyme

Answer 1

a) lack of processivity compared to DNA polymerase III

Dna pol V are Y family Dna polymerases. There are usually 3 categories of polymerases which are specific in different in functions. If we are not comparing Dna pol V with any other Dna Pol enzymes, then it is highly specific and best in fulfilling the purpose of translesion synthesis.

Negative effects- As processivity is also one of the key features which determines the rate of DNA synthesis through template, DNA POL V has no 3'-5' exonuclease activity. This makes it error prone.They have low catalytic efficiency, low processivity and low fidelity. So in terms of processivity , Dna Pol V do tend to have negative effects like inability to have high polymerization rate. It cannot bind more and faster number of nucleotides per sec on Dna template.

b) ability to accommodate bulky adducts in the active site of the enzyme

Positive effects- Dna pol V also known as umuD2'C polymerase is highly efficient in DNA replication machinery which allows Dna to replicate past Dna lesions such as thymine dimers. It replicate damaged DNA by bypassing damaged nucleotides. They binds such intercalators or bulky adducts as they cannot anymore causes hinderance in the activity of the enzyme and smoothly bypasses damaged nucleotides.

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