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Structure of the Receptor-Binding Carboxy-Terminal Domain of the Bacteriophage T5 L-Shaped Tail Fibre with and without Its Intra-Molecular Chaperone.

Abstract
Bacteriophage T5, a Siphovirus belonging to the order Caudovirales, has a flexible, three-fold symmetric tail, to which three L-shaped fibres are attached. These fibres recognize oligo-mannose units on the bacterial cell surface prior to infection and are composed of homotrimers of the pb1 protein. Pb1 has 1396 amino acids, of which the carboxy-terminal 133 residues form a trimeric intra-molecular chaperone that is auto-proteolyzed after correct folding. The structure of a trimer of residues 970-1263 was determined by single anomalous dispersion phasing using incorporated selenomethionine residues and refined at 2.3 Å resolution using crystals grown from native, methionine-containing, protein. The protein inhibits phage infection by competition. The phage-distal receptor-binding domain resembles a bullet, with the walls formed by partially intertwined beta-sheets, conferring stability to the structure. The fold of the domain is novel and the topology unique to the pb1 structure. A site-directed mutant (Ser1264 to Ala), in which auto-proteolysis is impeded, was also produced, crystallized and its 2.5 Å structure solved by molecular replacement. The additional chaperone domain (residues 1263-1396) consists of a central trimeric alpha-helical coiled-coil flanked by a mixed alpha-beta domain. Three long beta-hairpin tentacles, one from each chaperone monomer, extend into long curved grooves of the bullet-shaped domain. The chaperone-containing mutant did not inhibit infection by competition.
AuthorsCarmela Garcia-Doval, José R Castón, Daniel Luque, Meritxell Granell, José M Otero, Antonio L Llamas-Saiz, Madalena Renouard, Pascale Boulanger, Mark J van Raaij
JournalViruses (Viruses) Vol. 7 Issue 12 Pg. 6424-40 (Dec 08 2015) ISSN: 1999-4915 [Electronic] Switzerland
PMID26670244 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Molecular Chaperones
  • Mutant Proteins
  • Viral Tail Proteins
Topics
  • Caudovirales (chemistry, physiology)
  • Crystallography, X-Ray
  • Models, Molecular
  • Molecular Chaperones (chemistry, genetics)
  • Mutant Proteins (chemistry, genetics)
  • Protein Conformation
  • Siphoviridae (chemistry, physiology)
  • Viral Tail Proteins (chemistry, genetics)
  • Virus Attachment

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