Low processivity for DNA translocation by the ISWI molecular motor

Allen Eastlund, Gada Al-Ani, Christopher J. Fischer

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The motor protein ISWI (Imitation SWItch) is the conserved catalytic ATPase domain of the ISWI family of chromatin remodelers. Members of the ISWI family are involved in regulating the structure of cellular chromatin during times of transcription, translation, and repair. Current models for the nucleosome repositioning activity of ISWI and other chromatin remodelers require the translocation of the remodeling protein along double-stranded DNA through an ATP-dependent mechanism. Here we report results from spectrofluorometric stopped-flow experiments which demonstrate that ISWI displays very low processivity for free DNA translocation. By combining these results with those from experiments monitoring the DNA stimulated ATPase activity of ISWI we further demonstrate that the DNA translocation by ISWI is tightly coupled to ATP hydrolysis. The calculated coupling efficiency of 0.067 ± 0.018 ATP/ISWI/bp is seemingly quite low in comparison to similar DNA translocases and we present potential models to account for this. Nevertheless, the tight coupling of ATP hydrolysis to DNA translocation suggests that DNA translocation is not energetically rate limiting for nucleosome repositioning by ISWI.

Original languageEnglish (US)
Pages (from-to)1487-1493
Number of pages7
JournalBiochimica et Biophysica Acta - Proteins and Proteomics
Issue number10
StatePublished - Oct 24 2015

Bibliographical note

Funding Information:
Additionally, we would like to thank the University of Kansas General Research Fund ( 2301651 ) for the financial support.

Publisher Copyright:
© 2015 Elsevier B.V. All rights reserved.


  • Chromatin
  • ISWI
  • Kinetics
  • Proteins
  • Remodel
  • Stopped-flow


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