title: Partitivirus structure reveals a 120-subunit, helix-rich capsid with distinctive surface arches formed by quasisymmetric coat-protein dimers.
abstract: Two distinct partitiviruses, Penicillium stoloniferum viruses S and F, can be isolated from the fungus Penicillium stoloniferum. The bisegmented dsRNA genomes of these viruses are separately packaged in icosahedral capsids containing 120 coat-protein subunits. We used transmission electron cryomicroscopy and three-dimensional image reconstruction to determine the structure of Penicillium stoloniferum virus S at 7.3 A resolution. The capsid, approximately 350 A in outer diameter, contains 12 pentons, each of which is topped by five arched protrusions. Each of these protrusions is, in turn, formed by a quasisymmetric dimer of coat protein, for a total of 60 such dimers per particle. The density map shows numerous tubular features, characteristic of alpha helices and consistent with secondary structure predictions for the coat protein. This three-dimensional structure of a virus from the family Partitiviridae exhibits both similarities to and differences from the so-called "T = 2" capsids of other dsRNA viruses.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0378, USA.
authors.forename: Wendy F
authors.initials: WF
authors.lastname: Ochoa
authors.forename: Wendy M
authors.initials: WM
authors.lastname: Havens
authors.forename: Robert S
authors.initials: RS
authors.lastname: Sinkovits
authors.forename: Max L
authors.initials: ML
authors.lastname: Nibert
authors.forename: Said A
authors.initials: SA
authors.lastname: Ghabrial
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Baker
mesh_terms: D000595:Amino Acid Sequence; D002213:Capsid / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D036022:Capsid Proteins / Q000737:chemistry*; D020285:Cryoelectron Microscopy; D019281:Dimerization; D021621:Imaging, Three-Dimensional; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010407:Penicillium / Q000821:virology*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012328:RNA Viruses / Q000737:chemistry*; D012330:RNA, Double-Stranded / Q000737:chemistry; D014771:Virion / Q000302:isolation & purification
chemical_list: D036022:Capsid Proteins; D012330:RNA, Double-Stranded