Topoisomerases are the main enzymes capable of resolving the topological constraints imposed by DNA transactions such as transcription or replication. All bacteria possess topoisomerases of different types. Although bacteria with circular replicons should encounter similar DNA topology issues, the distribution of topoisomerases varies from one bacterium to another, suggesting polymorphic functioning. Recently, several proteins restricting, enhancing or modifying the activity of topoisomerases were discovered, opening the way to a new area of understanding DNA topology management during the bacterial cell cycle. In this review, we discuss the distribution of topoisomerases across the bacterial phylum and current knowledge on the interplay among the different topoisomerases to maintain topological homeostasis.
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Cover Image
Cover Image
The image depicts an artistic representation of the lift-out and sectioning step with a focused ion beam (FIB), which is referred to as serial lift-out. A block of vitreously frozen biological material (in this case, a single C. elegans L1 larva) is attached (or "welded") to a micromanipulator needle. The underside of the block is then attached to a rectangular mesh copper EM grid, and a section of ~1 µm is cut away from it with the FIB. This procedure is repeated, yielding an array of sections that can be further thinned to ~200 nm for cryo-ET and further structural analysis. Image hand drawn (ink), digitised and coloured with Adobe Fresco (iPad). Read more in 'Cryo-electron tomography: en route to the molecular anatomy of organisms and tissues' by Plitzko and colleagues on pp 2415-2425 of this issue of Biochemical Society Transactions. Image courtesy of JM Plitzko
Untangling bacterial DNA topoisomerases functions
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