Desirazu, RN and Prasad, Y Desirazu, RN and Prasad, Y, eds (2021) DNA recognition/processing: DNA restriction and modification: Type III enzymes. Elsevier, pp. 493-500. ISBN 978-012819460
Full text not available from this repository.Abstract
Restriction–modification (R–M) systems are defense systems in prokaryotes that protect them from foreign DNA. They were originally discovered as DNA cleaving enzymes that restricted infection by bacteriophages. There are around 1150 confirmed or putative type III restriction–modification (R–M) systems known to date, widely distributed among bacteria and archaea. To date, 13 members of this class of enzymes have been studied to some extent. Type III R–M systems consists of Mod and Res subunits. Mod subunits form a homodimeric Mod2 MTase complex that can recognize specific sequences and methylate DNA, whereas the subunits together can form a Mod2Res1 complex that cleaves DNA. Information regarding the mechanism of action of type III restriction complexes has been obtained chiefly from the dissection of EcoP15I and EcoP1I restriction enzymes. ATP hydrolysis is necessary for DNA cleavage by type III restriction enzymes. In several pathogenic bacteria the mod genes are known to harbor simple sequence repeats that are amenable to phase variation by slipped-strand mispairing. This discovery has paved the way for the delineation of a regulatory mechanism where switching between the ON and OFF status of the MTase alters the methylome of the organism. It has been shown that these phase variable regulons or phasevarions provide significant adaptability to these pathogenic bacteria and could be a substitute for global transcriptional regulators.
| Item Type: | Book |
|---|---|
| Publication: | Encyclopedia of Biological Chemistry: Third Edition |
| Publisher: | Elsevier |
| Additional Information: | The copyright for this article belongs to Elsevier |
| Keywords: | Adenine methylationATPaseDNA cleavageDNA loopingDNA translocationEpigeneticsMolecular machinesPhase variationRestriction–ModificationSMRT sequencing |
| Department/Centre: | Division of Chemical Sciences > Solid State & Structural Chemistry Unit |
| Date Deposited: | 22 Nov 2021 09:45 |
| Last Modified: | 22 Nov 2021 09:45 |
| URI: | http://eprints.iisc.ac.in/id/eprint/70567 |
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