TY - JOUR

T1 - The QTK Loop is Essential for the Communication between the N-Terminal ATPase Domain and the Central Cleavage-Ligation Region in Human Topoisomerase IIα

AU - Bendsen, Simon

AU - Oestergaard, Vibe H.

AU - Skouboe, Camilla

AU - Brinch, Marie

AU - Knudsen, Birgitta R.

AU - Andersen, Anni H.

PY - 2009

Y1 - 2009

N2 - We have characterized a human topoisomerase IIα enzyme with a deletion of the conserved QTK loop, which extends from the transducer domain to the ATP-binding pocket in the GHKL domain. The loop has been suggested to play a role for interdomain communication in type II topoisomerases. The mutant enzyme performs only very low levels of strand passage, although it is able to cleave and ligate DNA as well as close the N-terminal clamp. Cleavage is nearly unaffected by ATP and ATP analogues relative to the wild-type enzyme. Although the enzyme is able to close the clamp, the clamp has altered characteristics, allowing trapping of DNA also in the absence of an ATP analogue. The enzyme furthermore retains intrinsic levels of ATPase activity, but the activity is not stimulated by DNA. Our observations demonstrate that the QTK loop is an important player for the interdomain communication in human topoisomerase IIα. First, the loop seems to play a role in keeping the N-terminal clamp in an open conformation when no nucleotide is present. Once the nucleotide binds, it facilitates clamp closure, although it is not essential for this event. The QTK loop, in contrast, is essential for the DNA-stimulated ATPase activity of human topoisomerase IIα.

AB - We have characterized a human topoisomerase IIα enzyme with a deletion of the conserved QTK loop, which extends from the transducer domain to the ATP-binding pocket in the GHKL domain. The loop has been suggested to play a role for interdomain communication in type II topoisomerases. The mutant enzyme performs only very low levels of strand passage, although it is able to cleave and ligate DNA as well as close the N-terminal clamp. Cleavage is nearly unaffected by ATP and ATP analogues relative to the wild-type enzyme. Although the enzyme is able to close the clamp, the clamp has altered characteristics, allowing trapping of DNA also in the absence of an ATP analogue. The enzyme furthermore retains intrinsic levels of ATPase activity, but the activity is not stimulated by DNA. Our observations demonstrate that the QTK loop is an important player for the interdomain communication in human topoisomerase IIα. First, the loop seems to play a role in keeping the N-terminal clamp in an open conformation when no nucleotide is present. Once the nucleotide binds, it facilitates clamp closure, although it is not essential for this event. The QTK loop, in contrast, is essential for the DNA-stimulated ATPase activity of human topoisomerase IIα.

U2 - 10.1021/bi9005978

DO - 10.1021/bi9005978

M3 - Journal article

C2 - 19485418

AN - SCOPUS:67650090649

VL - 48

SP - 6508

EP - 6515

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 27

ER -