title: Crystal structure of Bacillus subtilis SPP1 phage gp23.1, a putative chaperone.
abstract: SPP1 is a siphophage infecting the gram-positive bacterium Bacillus subtilis. The SPP1 tail electron microscopy (EM) reconstruction revealed that it is mainly constituted by conserved structural proteins such as the major tail proteins (gp17.1), the tape measure protein (gp18), the Distal tail protein (Dit, gp19.1), and the Tail associated lysin (gp21). A group of five small genes (22-24.1) follows in the genome but it remains to be elucidated whether their protein products belong or not to the tail. Noteworthy, an unassigned EM density accounting for ~245 kDa is present at the distal end of the SPP1 tail-tip. We report here the gp23.1 crystal structure at 1.6 A resolution, a protein that lacks sequence identity to any known protein. We found that gp23.1 forms a hexamer both in the crystal lattice and in solution as revealed by light scattering measurements. The gp23.1 hexamer does not fit well in the unassigned SPP1 tail-tip EM density and we hypothesize that this protein might act as a chaperone.
authors.affiliation: Architecture et Fonction des Macromolécules Biologiques, UMR 6098 CNRS and Universités d'Aix-Marseille I & II, Marseille, France.
authors.forename: David
authors.initials: D
authors.lastname: Veesler
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Blangy
authors.forename: Julie
authors.initials: J
authors.lastname: Lichière
authors.forename: Miguel
authors.initials: M
authors.lastname: Ortiz-Lombardía
authors.forename: Paulo
authors.initials: P
authors.lastname: Tavares
authors.forename: Valérie
authors.initials: V
authors.lastname: Campanacci
authors.forename: Christian
authors.initials: C
authors.lastname: Cambillau
mesh_terms: D017103:Bacillus Phages / Q000737:chemistry* / Q000378:metabolism; D001412:Bacillus subtilis / Q000821:virology*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism; D055503:Protein Multimerization; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D018832:Molecular Chaperones; D014764:Viral Proteins