Tuesday, 20 August 2019 13:30

The structure of the bacteriophage T7 portal protein reveals a key mechanism in viral infection

  • This study identifies the opening and closing mechanism for T7 portal protein during the viral DNA translocation process
  • Researchers have used a combination of cryo electron microscopy and crystallography techniques to study this virus

Nature Communications publishes the result of the collaboration between several research groups belonging to the Spanish Council for Scientific Research (CSIC) on the structure and function of the bacteriophage T7 portal protein. Experts in cryo electron microscopy of the National Center for Biotechnology (CSIC), directed by José L. Carrascosa, and in X-ray crystallography of the Institute of Molecular Biology of Barcelona (CSIC), the Institute of Biomedical Research (IRB Barcelona), and the Center Biological Research (CSIC), directed by Miquel Coll, have worked together to combine both techniques, obtaining new data on the mechanism of action of this protein in the process of viral maturation.

“Bacteriophages are viruses that infect bacteria. In addition to their interest as a biological model because of their genetic simplicity but great structural complexity, they are now a new focus of attention for researchers given their potential as an alternative to the use of antibiotics, ”explains José L. Carrascosa, a researcher at the National Center for Biotechnology and co-director of work.

During the infection cycle of T7, a viral capsid is formed where the virus needs to include its genetic material, introducing it through a small entrance channel formed by the portal protein that is subsequently closed with the virus's tail protein. Until now it was unknown which was the mechanism that allowed to open and close this "door" in a controlled manner.

Ana Cuervo, first author of the work, together with Montserrat Fàbrega-Ferrer from IBMB and the IRB Barcelona, ​​highlights how “cryoelectron microscopy and its complementation with crystallography techniques allow not only to solve the atomic structure of large complexes that pose a technical challenge, but also to define a model of opening and closing the portal during the process of translocation of the viral DNA ”. Using this approach, researchers have been able to identify the interactions between the different proteins that allow changes in the conformation of the complex, from an open structure to allow the passage of viral DNA to a closed one when forming mature viral particles. 

This work has been funded by “Severo Ochoa” and “María de Maeztu” excellence programs, the “Ramón y Cajal” program of the Ministry of Science, Innovation and Universities, and the European iNEXT and Instruct-ERIC projects.

More information

Ana Cuervo, Montserrat Fàbrega-Ferrer, Cristina Machón, José Javier Conesa, Francisco José Javier Fernández, Rosa Pérez-Luque, Mar Pérez-Ruiz, Joan Pous, María Cristina Vega, José L. Carrascosa y Miquel Coll. Structures of T7 bacteriophage portal and tail suggest a viral DNA retention and ejection mechanism. Nature Communications. DOI: 10.1038/s41467-019-11705-9

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