title: Crystal structure of ORF12 from Lactococcus lactis phage p2 identifies a tape measure protein chaperone.
abstract: We report here the characterization of the nonstructural protein ORF12 of the virulent lactococcal phage p2, which belongs to the Siphoviridae family. ORF12 was produced as a soluble protein, which forms large oligomers (6- to 15-mers) in solution. Using anti-ORF12 antibodies, we have confirmed that ORF12 is not found in the virion structure but is detected in the second half of the lytic cycle, indicating that it is a late-expressed protein. The structure of ORF12, solved by single anomalous diffraction and refined at 2.9-A resolution, revealed a previously unknown fold as well as the presence of a hydrophobic patch at its surface. Furthermore, crystal packing of ORF12 formed long spirals in which a hydrophobic, continuous crevice was identified. This crevice exhibited a repeated motif of aromatic residues, which coincided with the same repeated motif usually found in tape measure protein (TMP), predicted to form helices. A model of a complex between ORF12 and a repeated motif of the TMP of phage p2 (ORF14) was generated, in which the TMP helix fitted exquisitely in the crevice and the aromatic patches of ORF12. We suggest, therefore, that ORF12 might act as a chaperone for TMP hydrophobic repeats, maintaining TMP in solution during the tail assembly of the lactococcal siphophage p2.
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: Marina
authors.initials: M
authors.lastname: Siponen
authors.forename: Giuliano
authors.initials: G
authors.lastname: Sciara
authors.forename: Manuela
authors.initials: M
authors.lastname: Villion
authors.forename: Silvia
authors.initials: S
authors.lastname: Spinelli
authors.forename: Julie
authors.initials: J
authors.lastname: Lichière
authors.forename: Christian
authors.initials: C
authors.lastname: Cambillau
authors.forename: Sylvain
authors.initials: S
authors.lastname: Moineau
authors.forename: Valérie
authors.initials: V
authors.lastname: Campanacci
mesh_terms: D017901:Bacteriophage P2 / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D013294:Lactococcus lactis / Q000821:virology*; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D014764:Viral Proteins