5mf2: Difference between revisions

The tail of Caudovirales bacteriophages serves as an adsorption device, a host cell wall-perforating machine and a genome delivery pathway. In Siphoviridae, the assembly of the long and flexible tail is a highly cooperative and regulated process that is initiated from the proteins forming the distal tail tip complex. In Gram-positive infecting siphophages, the Distal tail (Dit) protein has been structurally characterised, and is proposed to represent a baseplate hub docking structure. It is organised as a hexameric ring that connects the tail tube and the adsorption device. In this study we report the characterisation of pb9, a tail tip protein of Escherichia coli bacteriophage T5. By immunolocalisation we show that pb9 is located in the upper cone of T5 tail tip, at the end of the tail tube. The crystal structure of pb9 reveals a two-domain protein. Domain A exhibits remarkable structural similarity with the N-terminal domain of known Dit proteins, while domain B adopts an Oligosaccharide/oligonucleotide Binding-fold (OB-fold) that is not shared by these proteins. We thus propose that pb9 is the Dit protein of T5, making it the first Dit protein described for a Gram-negative infecting siphophages. Multiple sequence alignments suggest that pb9 is a paradigm for a large family of Dit proteins of siphopages infecting mostly gram-negative hosts. The modular structure of the Dit protein maintains the basic building block that would be conserved among all siphophages, combining it with a more divergent domain that might serve specific host adhesion properties.

Crystal structure of pb9, the distal tail protein of bacteriophage T5: A conserved structural motif among all siphophages.,Flayhan A, Vellieux FM, Lurz R, Maury O, Contreras-Martel C, Girard E, Boulanger P, Breyton C J Virol. 2013 Oct 23. PMID:24155371<ref>PMID:24155371</ref>