present: Prof. Sylvain Moineau, Université Laval, Québec, Canada ; Prof Douwe van Sinderen, Université de Cork, Irlande ; Dr. Paulo Tavares, CNRS CNRS Centre National de la Recherche Scientifique , Gif-sur-Yvette.
past: Prof. Marin van Heel, Imperial College, Londres, Grande Bretagne ; Dr. Patrick Bron, CBS Montpellier, France.
We have recently solved the crystal structure of the baseplate of lactophage p2 at 2.6 Å resolution. We have also determined its structure by cryo-electron microscopy (PMID:20351260) . The core of this baseplate, which has a total mass of 1 MDa, is made of three proteins coded by the genes orf15, orf16 and orf18. The orf18 codes the protein responsible for the recognition and adsorption to the host (RBP, Receptor Binding Protein). To produce a viable complex, we cloned these genes in tandem, as a pseudo-operon. Our first structure presented an unexpected conformation, since the binding domaines of the RBPs were pointing towards the head of the phage and not towards the host. At this point, a second structure, obtained in the presence of calcium, showed the expected conformation, allowing us to produce a hypothesis explaining the two-step mechanism of adsorption.