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A novel nuclease is the executing part of a bacterial plasmid defense system

de Manuela Weiß, Giacomo Giacomelli, Mathilde Ben Assaya, Finja Grundt, Ahmed Haouz, Feng Peng, Stéphanie Petrella, Anne Marie Wehenkel e Marc Bramkamp

Publicado: 6 de outubro de 2022
Servidor: bioRxiv
DOI: 10.1101/2022.10.06.511153

Resumo

Cells are continuously facing the risk of taking up foreign DNA that can compromise genomic and cellular integrity. Therefore, bacteria are in a constant arms race with mobile genetic elements such as phages, transposons and plasmids. They have developed several active strategies against invading DNA molecules that can be seen as a bacterial ‘innate immune system’. Anti-phage systems are usually organized in ‘defense islands’ and can consist of restriction-modification (R-M) systems, CRISPR-Cas, and abortive infection (Abi) systems. Despite recent advances in the field, much less is known about plasmid defense systems. We have recently identified the MksBEFG system in Corynebacterium glutamicum as a novel plasmid defense system which comprises homologues of the condensin system MukFEB. Here, we investigated the molecular arrangement of the MksBEFG complex. Importantly, we identified MksG as a novel nuclease that degrades plasmid DNA and is, thus, the executing part of the system. The crystal structure of MksG revealed a dimeric assembly through its DUF2220 C-terminal domains. This domain is homologous to the TOPRIM domain of the topoisomerase II family of enzymes and contains the corresponding divalent ion binding site that is essential for DNA cleavage in topoisomerases, explaining the in vitro nuclease activity of MksG. We further show that the MksBEF subunits exhibit an ATPase cycle similar to MukBEF in vitro and we reason that this reaction cycle, in combination with the nuclease activity provided by MksG, allows for processive degradation of invading plasmids. Super-resolution localization microscopy revealed that the Mks system is spatially regulated via to the polar scaffold protein DivIVA. Introduction of plasmids increases the diffusion rate and alters the localization of MksG, indicating an activation of the system in vivo .

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Avaliação PREreview de ambre jousselin et al.

De autoria de ambre jousselin, Gauthier Chauvin, Cédric Coupet, Marie Dewailly, Chloé Garcia, Marius Lorendeau, Mathias Orlando, Marvin Ramos-Hue, Virgile Rose, Esther Pouzet, Marion Tassoni, Sylvain Vicente e Peter Redder

Chauvin Gauthier, Coupet Cédric, Dewailly Marie, Garcia Chloé, Lorendeau Marius, Orlando Mathias, Ramos-Hue Marvin, Rose Virgile, Pouzet Esther, Rose Virgile, Tassoni Marion, Vicente Sylvain, Jousselin Ambre, Redder Peter

Université Toulouse Paul Sabatier, Master Microbiologie Moléculaire
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