Question

Briefly discuss the roles of the key enzymes and proteins involved in DNA replication in E.coli. In conclusion to your answer, describe the

         arrangement of these factors in the holenzyme complex at the E.coli DNA replication fork

Answer 1

Answer=

The roles of the key enzymes and proteins involved in DNA replication in E.coli as follows:

1.Helicase = Helicase effect strand separation at the forks.They separates the two strands of DNA at the replication fork behind the topoisomerase.

2. DNA polymerases : DNA polymerases are enzymes that synthesize DNA molecules from deoxyribonucleotides,the building blocks of DNA.

- These enzymes are essential to DNA replication and usually work in pairs to create two identical DNA strands from a single original DNA molecule.

DNA polymerase I = Filling if gap after removal RNA primer, DNA repair,removal of RNA primers.

DNA polymerase II = DNA repair.

DNA polymerase III = replication,proofreading and editing.

3.Single stranded Binding proteins(SSBs) = SSBs prevent reannealing i.e. binding of complementary DNA sequences.

Protect the single-stranded DNA from being digested by nucleases, and prevent secondary structure formation.

4.Topoisomerase = Also called as DNA Gyrase and that act on the topology of DNA.

-Topoisomerases bind to double -stranded DNA and cut the phosphate backbone of either one or both the DNA strands, this intermediate break allows the DNA to be untangled or unwound.

5.DNA ligase = It facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.

6.Primase = DNA primase is an enzyme involved in the replication of DNA

- Primase catalyses the synthesis of a short RNA segment called a primer complementary to a ssDNA template.