Vaccinia DNA topoisomerase

Vaccinia DNA topoisomerase

Topoisomerase Enzymes have the capability to cleave and rejoin the strands of DNA by forming a 3’ phosphorylated intermediate & a conserved active site (tyrosine).

The Biological function of Topoisomerases is that they keep the topological formation of cellular state of DNA by terminating the supercoils which are made during the DNA replication & transcription.

Gene	TOP-1 ORF: H6R
Protein	DNA topoisomerase-1B
Organism	Vaccinia virus (VACV) Copenhagen Strain

Table [Classification]

Function of Vaccinia DNA topoisomerase

 It Release the supercoil and torsion tension of the DNA which is introduced by DNA replication & DNA transcription by rapidly cleaving and ligating 1 strand of DNA.

By introduction of trans-esterification, DNA strand is broken at a very specific site which is 5’(CT)CCTTp.

The Phosphodiester is then attacked by Tyrosine (catalytic) which result’s in

DNA-(3’phosphotyrosl)-Enzyme intermediate & the removal of 5’-OH strand of DNA.

The free strand of the DNA then go through the channel around the uninterrupted strand thus eliminating the DNA supercoils.

In the end the Re-ligation step involves attack of the DNA 5’-OH against covalent intermediate to terminate the active site tyrosine and reinstate the Phosphodiester backbone of DNA.

Additional information

Topoisomerase-1 from the vaccinia has the sequence & mechanic homologies/ similarities with the Eukaryotic topoisomerase type-1.