title: Crystal structure of bacteriophage SPP1 distal tail protein (gp19.1): a baseplate hub paradigm in gram-positive infecting phages.
abstract: Siphophage SPP1 infects the gram-positive bacterium Bacillus subtilis using its long non-contractile tail and tail-tip. Electron microscopy (EM) previously allowed a low resolution assignment of most orf products belonging to these regions. We report here the structure of the SPP1 distal tail protein (Dit, gp19.1). The combination of x-ray crystallography, EM, and light scattering established that Dit is a back-to-back dimer of hexamers. However, Dit fitting in the virion EM maps was only possible with a hexamer located between the tail-tube and the tail-tip. Structure comparison revealed high similarity between Dit and a central component of lactophage baseplates. Sequence similarity search expanded its relatedness to several phage proteins, suggesting that Dit is a docking platform for the tail adsorption apparatus in Siphoviridae infecting gram-positive bacteria and that its architecture is a paradigm for these hub proteins. Dit structural similarity extends also to non-contractile and contractile phage tail proteins (gpV(N) and XkdM) as well as to components of the bacterial type 6 secretion system, supporting an evolutionary connection between all these devices.
authors.affiliation: Architecture et Fonction des Macromolécules Biologiques, UMR 6098 CNRS and Universités d'Aix-Marseille I & II, Campus de Luminy, Case 932, 13288 Marseille Cedex 09, France.
authors.forename: David
authors.initials: D
authors.lastname: Veesler
authors.forename: Gautier
authors.initials: G
authors.lastname: Robin
authors.forename: Julie
authors.initials: J
authors.lastname: Lichière
authors.forename: Isabelle
authors.initials: I
authors.lastname: Auzat
authors.forename: Paulo
authors.initials: P
authors.lastname: Tavares
authors.forename: Patrick
authors.initials: P
authors.lastname: Bron
authors.forename: Valérie
authors.initials: V
authors.lastname: Campanacci
authors.forename: Christian
authors.initials: C
authors.lastname: Cambillau
mesh_terms: D001412:Bacillus subtilis / Q000821:virology*; D001435:Bacteriophages / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D011487:Protein Conformation; D017906:Siphoviridae / Q000235:genetics*; D054334:Viral Regulatory and Accessory Proteins; D017376:Viral Tail Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014771:Virion / Q000378:metabolism
chemical_list: D054334:Viral Regulatory and Accessory Proteins; D017376:Viral Tail Proteins; C073671:SPP1 pac region protein, Bacteriophage SPP1