Lecture 5 DNA topoisomerases

Question 1

How do DNA topo cleave bonds

Answer 1

forms reversible convalent enzyme-DNA adduct

(phosphodiester line

Question 2

Differences in types of Topo1

Answer 2

Type 1A- link at 5’ phosphate

Type 1B- Link at 3’ end

Question 3

How does it relax DNA

Answer 3

Binds to one strand of DNA, moves active site tyrosine into place at respective end and cleavage happens by phosphodiester linkage.
Gap is opened up via opening of clamp mediated by the flexible hinge domains
Strand passes through and clamp closes and religates.
Protein opens and closes again to release strand`