Adsorption of lactococcal phages to the host cell wall : the structures and functions of their baseplates
Vendredi 4 avril 2014 11:00
- Duree : 1 heure
Lieu : Salle des séminaires de l’IBS - 6 rue Jules Horowitz - Grenoble
Orateur : Christian CAMBILLAU (Laboratoire Architecture et Fonction des Macromolécules Biologiques (AFMB), Marseille)
Siphoviridae, the most abundant viral family on earth, infects bacteria as well as archaea. All known siphophages infecting gram+ Lactococcus lactis possess a baseplate at the tip of their tail,
involved in host recognition and attachment. We have reported the analysis of p2 phage baseplate structure by X-ray crystallography and electron microscopy and we proposed a mechanism for its
activation during attachment to the host cell. This 1 MDa, E.coli-expressed baseplate is composed of three protein species, including six trimers of the receptor binding protein (RBP). RBPs host-recognition
domains point upwards, towards the capsid, in agreement with the electron-microscopy map of the virion. In the presence of Ca2+, a cation mandatory for p2 infection, the RBPs rotated 200° downwards,
presenting their binding sites to the host, and a channel opens at the bottom of the baseplate for DNA passage. In contrast, phage TP901-1 BP harbors 54 RBPs to mediate host anchoring. The crystal
structure of TP901-1 BP (MW 1.8 Mda) has been solved at 3.9 resolution. It exhibits an infection-ready conformation, independant of Ca2+, and differs strikingly from lactococcal phage p2. The comparison
of several Siphoviridae structures uncovers a close organization of their central core, while striking differences occur at the periphery of their BPs, leading to different mechanisms of host recognition and
infection.
Contact : odile.kaikati@ibs.fr
Discipline évènement : (Biologie / Chimie)
Entité organisatrice : (IBS)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire IBS)
Site de l'évènement : Polygone scientifique
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