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Front. Mol. Biosci. | doi: 10.3389/fmolb.2018.00017

Relaxase MobM Induces a Molecular Switch at its Cognate Origin of Transfer

  • 1Departamento de Bioquímica, Microbiología, Biología Celular y Genética, Universidad de La Laguna, Spain
  • 2Unidad de Investigacion, Hospital Universitario de La Candelaria, Hospital Universitario Nuestra Señora de Candelaria, Spain
  • 3Centro de Investigaciones Biológicas (CSIC), Spain

The MOBV1 family of relaxases is broadly distributed in plasmids and other mobile genetic elements isolated from staphylococci, enterococci, and streptococci. The prototype of this family is protein MobM encoded by the streptococcal promiscuous plasmid pMV158. MobM cleaves the phosphodiester bond of a specific dinucleotide within the origin of transfer (oriT) to initiate the conjugative transfer. Differently from other relaxases, MobM and probably other members of the family cleaves its target single-stranded DNA through a histidine residue rather than the commonly used tyrosine. The oriT of the MOBV1 family differs from other well-known conjugative systems since it has sequences with three inverted repeats, which were predicted to generate three mutually-exclusive hairpins on supercoiled DNA. In this work, such hypothesis was evaluated through footprinting experiments on supercoiled plasmid DNA. We have found a change in hairpin extrusion mediated by protein MobM. This conformational change involves a shift from the main hairpin generated on ‘naked’ DNA to a different hairpin in which the nick site is positioned in a single-stranded configuration. Our results indicate that the oriTpMV158 acts as a molecular switch in which, depending on the inverted repeat recognized by MobM, pMV158 mobilization could be turned ‘on’ or ‘off’.

Keywords: MobM relaxase, plasmid pMV158, DNA-protein interactions, hairpin formation, origin of transfer

Received: 22 Nov 2017; Accepted: 09 Feb 2018.

Edited by:

Emil Alexov, Clemson University, United States

Reviewed by:

Marko Djordjevic, Faculty of Biology, University of Belgrade, Serbia
Gloria Del Solar, Consejo Superior de Investigaciones Científicas (CSIC), Spain  

Copyright: © 2018 Lorenzo-Diaz, Fernandez-Lopez, Guillén-Guío, Bravo and Espinosa. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Dr. Alicia Bravo, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain, abravo@cib.csic.es
Prof. Manuel Espinosa, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain, mespinosa@cib.csic.es