5aq5
From Proteopedia
Structure of the Carboxy-Terminal Domain of the Bacteriophage T5 L- Shaped Tail Fibre
Structural highlights
Function[FIBL_BPT5] Assembles together with p132 to form the three L-shaped long tail fibers that recognize the host lipopolysaccharides that serve as adhesion receptor for virus entry. P132 makes the proximal part and pb8 the distal part that binds to the host cell surface. The L-shaped long tail fibers are attached to a collar structure at the junction between the tail tube and the conical tail tip. Each fiber consists of a thin proximal rod of about 30 nm connected by a hinge to a thicker distal part of about 47 nm.[1] [2] Publication Abstract from PubMedBacteriophage 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 A 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 A 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. Structure of the Receptor-Binding Carboxy-Terminal Domain of the Bacteriophage T5 L-Shaped Tail Fibre with and without Its Intra-Molecular Chaperone.,Garcia-Doval C, Caston JR, Luque D, Granell M, Otero JM, Llamas-Saiz AL, Renouard M, Boulanger P, van Raaij MJ Viruses. 2015 Dec 8;7(12):6424-40. doi: 10.3390/v7122946. PMID:26670244[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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