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Etudes par cryo-microscopie électronique de la structure de virus : application aux bactériophages Gifsy-2 de Salmonella Typhimirium et T5 d'Escherichia Coli

Abstract : Bacteriophage genomes are distinctly mosaic, and as more structures are solved, the phage morphologies also demonstrate a mosaic pattern. In a first project, we have solved capsid structures for several maturation intermediates of Gifsy-2, a phage infecting the bacteria Salmonella, by cryo-electron microscopy to resolutions up to 12 Ångstroms. On the genetic level we observe a long gene encoding the mature gifsy-2 capsid protein at the C-terminal end, and find striking homology with the Clp-P protease at the N-terminus including alignment of the catalytic triad. By analogy with related phage genomes the central domain encoding ~200 amino acids is expected to have scaffolding and/or decoration functions. This unique gene structure gives rise to a capsid maturation pathway that engages features from phages ? and HK97. In a second project, we have determined the E.Coli phage T5 structures of the icosahedral capsid to 19 Ångstroms resolution and the helical tail to ~30Å. We confirm the unusual trimeric symmetry of the tail tube. The capsid is composed of pentamers and hexamers of pb8 arranged with triangulation number t=13 and we localize the pb10 decoration protein to the exterior surface of the hexamers. Sequence comparison between pb8 and the HK97 capsid protein, together with modeling of the T5 capsid with HK97 atomic model, suggests that the T5 capsid likely adopts the same capsid protein fold as its smaller sibling, differing in size by the inclusion of additional hexamers. We propose that the precursor N-terminal domain of pb8 is involved in initial capsid assembly, as for HK97, specifically directing construction of the appropriately sized capsid.
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https://tel.archives-ouvertes.fr/tel-00011108
Contributor : Gregory Effantin <>
Submitted on : Thursday, November 24, 2005 - 5:35:00 PM
Last modification on : Wednesday, November 4, 2020 - 2:16:06 PM
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Grégory Effantin. Etudes par cryo-microscopie électronique de la structure de virus : application aux bactériophages Gifsy-2 de Salmonella Typhimirium et T5 d'Escherichia Coli. Biophysique [physics.bio-ph]. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00011108⟩

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