title: Three-dimensional reconstructions of the bacteriophage CUS-3 virion reveal a conserved coat protein I-domain but a distinct tailspike receptor-binding domain.
abstract: CUS-3 is a short-tailed, dsDNA bacteriophage that infects serotype K1 Escherichia coli. We report icosahedrally averaged and asymmetric, three-dimensional, cryo-electron microscopic reconstructions of the CUS-3 virion. Its coat protein structure adopts the "HK97-fold" shared by other tailed phages and is quite similar to that in phages P22 and Sf6 despite only weak amino acid sequence similarity. In addition, these coat proteins share a unique extra external domain ("I-domain"), suggesting that the group of P22-like phages has evolved over a very long time period without acquiring a new coat protein gene from another phage group. On the other hand, the morphology of the CUS-3 tailspike differs significantly from that of P22 or Sf6, but is similar to the tailspike of phage K1F, a member of the extremely distantly related T7 group of phages. We conclude that CUS-3 obtained its tailspike gene from a distantly related phage quite recently.
authors.affiliation: Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, CA 92093-0378, United States. Electronic address: kparent@msu.edu.
authors.forename: Kristin N
authors.initials: KN
authors.lastname: Parent
authors.affiliation: Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, CA 92093-0378, United States.
authors.forename: Jinghua
authors.initials: J
authors.lastname: Tang
authors.affiliation: Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, CA 92093-0378, United States.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cardone
authors.affiliation: University of Utah School of Medicine, Division of Microbiology and Immunology, Department of Pathology, Salt Lake City, UT 84112, United States.
authors.forename: Eddie B
authors.initials: EB
authors.lastname: Gilcrease
authors.affiliation: Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, CA 92093-0378, United States.
authors.forename: Mandy E
authors.initials: ME
authors.lastname: Janssen
authors.affiliation: Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, CA 92093-0378, United States.
authors.forename: Norman H
authors.initials: NH
authors.lastname: Olson
authors.affiliation: University of Utah School of Medicine, Division of Microbiology and Immunology, Department of Pathology, Salt Lake City, UT 84112, United States. Electronic address: sherwood.casjens@path.utah.edu.
authors.forename: Sherwood R
authors.initials: SR
authors.lastname: Casjens
authors.affiliation: Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, CA 92093-0378, United States; University of California, San Diego, Division of Biological Sciences, La Jolla, CA, 92093, United States. Electronic address: tsb@ucsd.edu.
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Baker
mesh_terms: D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D017124:Conserved Sequence; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014771:Virion / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D036022:Capsid Proteins
keywords: Bacteriophage; CUS-3; Cryo-electron microscopy; Virion structure