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Structural Insights into Lactococcal Siphophage p2 Baseplate Activation Mechanism

Virulent phages infecting L. lactis, an industry-relevant bacterium, pose a significant risk to the quality of the fermented milk products. Phages of the Skunavirus genus are by far the most isolated lactococcal phages in the cheese environments and phage p2 is the model siphophage for this viral ge...

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Autores principales: Spinelli, Silvia, Tremblay, Denise, Moineau, Sylvain, Cambillau, Christian, Goulet, Adeline
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7472080/
https://www.ncbi.nlm.nih.gov/pubmed/32796652
http://dx.doi.org/10.3390/v12080878
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author Spinelli, Silvia
Tremblay, Denise
Moineau, Sylvain
Cambillau, Christian
Goulet, Adeline
author_facet Spinelli, Silvia
Tremblay, Denise
Moineau, Sylvain
Cambillau, Christian
Goulet, Adeline
author_sort Spinelli, Silvia
collection PubMed
description Virulent phages infecting L. lactis, an industry-relevant bacterium, pose a significant risk to the quality of the fermented milk products. Phages of the Skunavirus genus are by far the most isolated lactococcal phages in the cheese environments and phage p2 is the model siphophage for this viral genus. The baseplate of phage p2, which is used to recognize its host, was previously shown to display two conformations by X-ray crystallography, a rested state and an activated state ready to bind to the host. The baseplate became only activated and opened in the presence of Ca(2+). However, such an activated state was not previously observed in the virion. Here, using nanobodies binding to the baseplate, we report on the negative staining electron microscopy structure of the activated form of the baseplate directly observed in the p2 virion, that is compatible with the activated baseplate crystal structure. Analyses of this new structure also established the presence of a second distal tail (Dit) hexamer as a component of the baseplate, the topology of which differs largely from the first one. We also observed an uncoupling between the baseplate activation and the tail tip protein (Tal) opening, suggesting an infection mechanism more complex than previously expected.
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spelling pubmed-74720802020-09-04 Structural Insights into Lactococcal Siphophage p2 Baseplate Activation Mechanism Spinelli, Silvia Tremblay, Denise Moineau, Sylvain Cambillau, Christian Goulet, Adeline Viruses Article Virulent phages infecting L. lactis, an industry-relevant bacterium, pose a significant risk to the quality of the fermented milk products. Phages of the Skunavirus genus are by far the most isolated lactococcal phages in the cheese environments and phage p2 is the model siphophage for this viral genus. The baseplate of phage p2, which is used to recognize its host, was previously shown to display two conformations by X-ray crystallography, a rested state and an activated state ready to bind to the host. The baseplate became only activated and opened in the presence of Ca(2+). However, such an activated state was not previously observed in the virion. Here, using nanobodies binding to the baseplate, we report on the negative staining electron microscopy structure of the activated form of the baseplate directly observed in the p2 virion, that is compatible with the activated baseplate crystal structure. Analyses of this new structure also established the presence of a second distal tail (Dit) hexamer as a component of the baseplate, the topology of which differs largely from the first one. We also observed an uncoupling between the baseplate activation and the tail tip protein (Tal) opening, suggesting an infection mechanism more complex than previously expected. MDPI 2020-08-11 /pmc/articles/PMC7472080/ /pubmed/32796652 http://dx.doi.org/10.3390/v12080878 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Spinelli, Silvia
Tremblay, Denise
Moineau, Sylvain
Cambillau, Christian
Goulet, Adeline
Structural Insights into Lactococcal Siphophage p2 Baseplate Activation Mechanism
title Structural Insights into Lactococcal Siphophage p2 Baseplate Activation Mechanism
title_full Structural Insights into Lactococcal Siphophage p2 Baseplate Activation Mechanism
title_fullStr Structural Insights into Lactococcal Siphophage p2 Baseplate Activation Mechanism
title_full_unstemmed Structural Insights into Lactococcal Siphophage p2 Baseplate Activation Mechanism
title_short Structural Insights into Lactococcal Siphophage p2 Baseplate Activation Mechanism
title_sort structural insights into lactococcal siphophage p2 baseplate activation mechanism
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7472080/
https://www.ncbi.nlm.nih.gov/pubmed/32796652
http://dx.doi.org/10.3390/v12080878
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