Type III restriction endonucleases are heterotrimeric: comprising one helicase-nuclease subunit and a dimeric methyltransferase that binds only one specific DNA

Annika Butterer, Christian Pernstich, Rachel M Smith, Frank Sobott, Mark D Szczelkun, Júlia Tóth

Research output: Contribution to journalArticle (Academic Journal)peer-review

21 Citations (Scopus)
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Abstract

Fundamental aspects of the biochemistry of Type III restriction endonucleases remain unresolved despite being characterized by numerous research groups in the past decades. One such feature is the subunit stoichiometry of these hetero-oligomeric enzyme complexes, which has important implications for the reaction mechanism. In this study, we present a series of results obtained by native mass spectrometry and size exclusion chromatography with multi-angle light scattering consistent with a 1:2 ratio of Res to Mod subunits in the EcoP15I, EcoPI and PstII complexes as the main holoenzyme species and a 1:1 stoichiometry of specific DNA (sDNA) binding by EcoP15I and EcoPI. Our data are also consistent with a model where ATP hydrolysis activated by recognition site binding leads to release of the enzyme from the site, dissociation from the substrate via a free DNA end and cleavage of the DNA. These results are discussed critically in the light of the published literature, aiming to resolve controversies and discuss consequences in terms of the reaction mechanism.

Original languageEnglish
Pages (from-to)5139-50
Number of pages12
JournalNucleic Acids Research
Volume42
Issue number8
Early online date1 Feb 2014
DOIs
Publication statusPublished - Apr 2014

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