Journal
NUCLEIC ACIDS RESEARCH
Volume 40, Issue 19, Pages 9774-9787Publisher
OXFORD UNIV PRESS
DOI: 10.1093/nar/gks704
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Funding
- EST early stage research scholarship
- EU FP7
- BBSRC, UK [BB/J004561/1]
- John Innes Foundation
- Biotechnology and Biological Sciences Research Council [BBS/E/J/00000201] Funding Source: researchfish
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DNA gyrase is the only type II topoisomerase in Mycobacterium tuberculosis and needs to catalyse DNA supercoiling, relaxation and decatenation reactions in order to fulfil the functions normally carried out by gyrase and DNA topoisomerase IV in other bacteria. We have obtained evidence for the existence of a Ca2+-binding site in the GyrA subunit of M. tuberculosis gyrase. Ca2+ cannot support topoisomerase reactions in the absence of Mg2+, but partial removal of Ca2+ from GyrA by dialysis against EGTA leads to a modest loss in relaxation activity that can be restored by adding back Ca2+. More extensive removal of Ca2+ by denaturation of GyrA and dialysis against EGTA results in an enzyme with greatly reduced enzyme activities. Mutation of the proposed Ca2+-binding residues also leads to loss of activity. We propose that Ca2+ has a regulatory role in M. tuberculosis gyrase and suggest a model for the modulation of gyrase activity by Ca2+ binding.
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