Structural investigations of a Podoviridae streptococcus phage C1, implications for the mechanism of viral entry

• Published in: Proceedings of the National Academy of Sciences - PNAS 2012-08, Vol.109 (35), p.14001-14006
• Main Authors: Aksyuk, Anastasia A, Bowman, Valorie D, Kaufmann, Bärbel, Fields, Christopher, Klose, Thomas, Holdaway, Heather A, Fischetti, Vincent A, Rossmann, Michael G
• Format: Article
• Language: English
• Subjects: Appendages; Bacteria; Bacteriophages; Biological Sciences; Capsid; Capsid - chemistry; Capsid - ultrastructure; Capsid proteins; Capsid Proteins - chemistry; Cell walls; Cells; coat proteins; cryo-electron microscopy; Cryoelectron Microscopy; Crystal structure; Crystallography, X-Ray; DNA; genome; Genomes; Myoviridae; Myoviridae - growth & development; Myoviridae - ultrastructure; Podoviridae; Podoviridae - growth & development; Podoviridae - ultrastructure; Protein Structure, Tertiary; Proteins; sequence homology; Siphoviridae; Streptococcus; Streptococcus - virology; Streptococcus Phages - growth & development; Streptococcus Phages - ultrastructure; structural proteins; Viral Structural Proteins - chemistry; Virus Replication - physiology; Viruses
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1207730109

The Podoviridae phage C1 was one of the earliest isolated bacteriophages and the first virus documented to be active against streptococci. The icosahedral and asymmetric reconstructions of the virus were calculated using cryo-electron microscopy. The capsid protein has an HK97 fold arranged into a T = 4 icosahedral lattice. The C1 tail is terminated with a φ 29-like knob, surrounded by a skirt of twelve long appendages with novel morphology. Several C1 structural proteins have been identified, including a candidate for an appendage. The crystal structure of the knob has an N-terminal domain with a fold observed previously in tube forming proteins of Siphoviridae and Myoviridae phages. The structure of C1 suggests the mechanisms by which the virus digests the cell wall and ejects its genome. Although there is little sequence similarity to other phages, conservation of the structural proteins demonstrates a common origin of the head and tail, but more recent evolution of the appendages.