The Structure of <i>Spiroplasma Virus 4</i>: Exploring the Capsid Diversity of the <i>Microviridae</i>
Mario Mietzsch,
Shweta Kailasan,
Antonette Bennett,
Paul Chipman,
Bentley Fane,
Juha T. Huiskonen,
Ian N. Clarke,
Robert McKenna
Affiliations
Mario Mietzsch
Department of Biochemistry and Molecular Biology, College of Medicine, Center for Structural Biology, McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
Shweta Kailasan
Department of Biochemistry and Molecular Biology, College of Medicine, Center for Structural Biology, McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
Antonette Bennett
Department of Biochemistry and Molecular Biology, College of Medicine, Center for Structural Biology, McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
Paul Chipman
Department of Biochemistry and Molecular Biology, College of Medicine, Center for Structural Biology, McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
Bentley Fane
The BIO5 Institute, Keating Building, University of Arizona, Tucson, AZ 85721, USA
Juha T. Huiskonen
Institute of Biotechnology, Helsinki Institute of Life Science HiLIFE, University of Helsinki, 00014 Helsinki, Finland
Ian N. Clarke
Molecular Microbiology Group, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK
Robert McKenna
Department of Biochemistry and Molecular Biology, College of Medicine, Center for Structural Biology, McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
Spiroplasma virus 4 (SpV4) is a bacteriophage of the Microviridae, which packages circular ssDNA within non-enveloped T = 1 icosahedral capsids. It infects spiroplasmas, which are known pathogens of honeybees. Here, the structure of the SpV4 virion is determined using cryo-electron microscopy to a resolution of 2.5 Å. A striking feature of the SpV4 capsid is the mushroom-like protrusions at the 3-fold axes, which is common among all members of the subfamily Gokushovirinae. While the function of the protrusion is currently unknown, this feature varies widely in this subfamily and is therefore possibly an adaptation for host recognition. Furthermore, on the interior of the SpV4 capsid, the location of DNA-binding protein VP8 was identified and shown to have low structural conservation to the capsids of other viruses in the family. The structural characterization of SpV4 will aid future studies analyzing the virus–host interaction, to understand disease mechanisms at a molecular level. Furthermore, the structural comparisons in this study, including a low-resolution structure of the chlamydia phage 2, provide an overview of the structural repertoire of the viruses in this family that infect various bacterial hosts, which in turn infect a wide range of animals and plants.
