Question

Q1 Schematically draw the covalent intermediates in Type IIA and IB
(read those designations carefully!) topoisomerase reactions with DNA.

Answer 1

Type IB solves the problem of overwound and underwound DNA through a hindered rotary mechanism.

Enzyme first wraps around DNA and creates a single,3' phosphotyrosine intermediate.The 5' end is then free to rotate, twisting it about the other strand,to relax DNA until the topoisomerase religates the broken strands.