Nucleotide sequence of the genome of the bacteriophage α3: interrelationship of the genome structure and the gene products with those of the phages, θX174, G4 and θK

Kodaira, Ken-Ichi; Nakano, Kazumi; Okada, Shoichi; Taketo, Akira

doi:10.1016/0167-4781(92)90440-b

Cited by 31 publications

(18 citation statements)

References 31 publications

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“…The viral coat proteins of Chp2 and Chp1 show the highest identity and are clearly related to the coat protein of SpV4. Homologies with the coat proteins of the Microviridae coliphages, X174, G4, and ␣3 (11,16,21) are considerably lower (20%). The SpV4 and X174 coat proteins display a major structural difference: in SpV4, a 71-amino-acid insertion loop forms "mushroom-like" protrusions at the threefold axis of symmetry (5).…”

Section: Discussionmentioning

confidence: 99%

Molecular Characterization of a Bacteriophage (Chp2) from Chlamydia psittaci

Liu

Everson

Fane

et al. 2000

J Virol

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Comparisons of the proteome of abortifacient Chlamydia psittaci isolates from sheep by two-dimensional gel electrophoresis identified a novel abundant protein with a molecular mass of 61.4 kDa and an isoelectric point of 6.41. C-terminal sequence analysis of this protein yielded a short peptide sequence that had an identical match to the viral coat protein (VP1) of the avian chlamydiaphage Chp1. Electron microscope studies revealed the presence of a 25-nm-diameter bacteriophage (Chp2) with no apparent spike structures. Thin sections of chlamydia-infected cells showed that Chp2 particles were located to membranous structures surrounding reticulate bodies (RBs), suggesting that Chp2 is cytopathic for ovine C. psittaci RBs. Chp2 double-stranded circular replicative-form DNA was purified and used as a template for DNA sequence analysis. The Chp2 genome is 4,567 bp and encodes up to eight open reading frames (ORFs); it is similar in overall organization to the Chp1 genome. Seven of the ORFs (1 to 5, 7, and 8) have sequence homologies with Chp1. However, ORF 6 has a different spatial location and no cognate partner within the Chp1 genome. Chlamydiaphages have three viral structural proteins, VP1, VP2, and VP3, encoded by ORFs 1 to 3, respectively. Amino acid residues in the X174 procapsid known to mediate interactions between the viral coat protein and internal scaffolding proteins are conserved in the Chp2 VP1 and VP3 proteins. We suggest that VP3 performs a scaffolding-like function but has evolved into a structural protein.

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Section: Discussionmentioning

confidence: 99%

Molecular Characterization of a Bacteriophage (Chp2) from Chlamydia psittaci

Liu

Everson

Fane

et al. 2000

J Virol

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“…The DNAs of nine members of the family, isolated from very diverse hosts (proteobacteria, Spiroplasma, and Chlamydia), have been sequenced (11,16,17,18,22,(24)(25)(26). The species falls into two distinct subfamilies, although the subfamilies are not officially recognized in the virus taxonomy.…”

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confidence: 99%

Microviridae , a Family Divided: Isolation, Characterization, and Genome Sequence of φMH2K, a Bacteriophage of the Obligate Intracellular Parasitic Bacterium Bdellovibrio bacteriovorus

et al. 2002

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A novel single-stranded DNA phage, MH2K, of Bdellovibrio bacteriovorus was isolated, characterized, and sequenced. This phage is a member of the Microviridae, a family typified by bacteriophage X174. Although B. bacteriovorus and Escherichia coli are both classified as proteobacteria, MH2K is only distantly related to X174. Instead, MH2K exhibits an extremely close relationship to the Microviridae of Chlamydia in both genome organization and encoded proteins. Unlike the double-stranded DNA bacteriophages, for which a wide spectrum of diversity has been observed, the single-stranded icosahedral bacteriophages appear to fall into two distinct subfamilies. These observations suggest that the mechanisms driving single-stranded DNA bacteriophage evolution are inherently different from those driving the evolution of the double-stranded bacteriophages.Bacteriophages have been isolated and characterized from a wide range of microorganisms for more than 80 years. The vast majority of these phages are large double-stranded DNA viruses, as typified by the lambdoid, T-odd and -even families (1). Recent advances in DNA sequencing technologies and bioinformatics have facilitated the study of double-stranded DNA bacteriophage evolution (13,14,28). From these and other studies, a clear picture has emerged (13, 14). The prevalence of double-stranded DNA phages and prophages-cryptic, defective, and replication competent-creates an enormous pool of evolutionary material for horizontal exchange. Consequently, a mosaic spectrum of related phage species has arisen.The icosahedral, single-stranded DNA phages, or Microviridae, appear to be less common than double-stranded DNA phages. The DNAs of nine members of the family, isolated from very diverse hosts (proteobacteria, Spiroplasma, and Chlamydia), have been sequenced (11,16,17,18,22,(24)(25)(26). The species falls into two distinct subfamilies, although the subfamilies are not officially recognized in the virus taxonomy. One is represented by X174 and contains the phages that propagate in proteobacteria. The other subfamily contains phages of Chlamydia and Spiroplasma. Although these two hosts are not closely related, their phages, Chp1, Chp2, and SpV4, respectively, are quite similar. The principal difference between the two subfamilies is the existence of two genes and the complexity of major coat protein. The Chlamydia and Spiroplasma phages do not encode major spike and external scaffolding proteins. Their more-complex coat proteins contain an insertion loop that forms large threefold-related protrusions (6). Protein homologies between the two subfamilies are approximately 20% or less (6), a typical value when comparing the most distantly related members of either the lambda or T4-like groups (14, 28). However, unlike tailed doublestranded DNA families, no mosaic species that bridge the evolutionary chasms have been isolated.While the available DNA sequences suggest that the evolution of Microviridae may differ from the evolution of the moreprevalent, double-stranded DNA phages,...

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“…As shown in Fig. 2, divergent residues are localized to two distinct regions within the D proteins: amino acids comprising ␣ helix 1 and the C terminus comprising loop 6 and the tip of ␣ helix 7 in the atomic structure (2,3,11,21). To determine whether one or both of these domains confer inhibitory effects, chimeric genes were constructed and the proteins were expressed in vivo.…”

Section: Resultsmentioning

confidence: 99%

Foreign and Chimeric External Scaffolding Proteins as Inhibitors of Microviridae Morphogenesis

Burch

Fane

2000

J Virol

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Viral assembly is an ideal system in which to investigate the transient recognition and interplay between proteins. During morphogenesis, scaffolding proteins temporarily associate with structural proteins, stimulating conformational changes that promote assembly and inhibit off-pathway reactions. Microviridae morphogenesis is dependent on two scaffolding proteins, an internal and an external species. The external scaffolding protein is the most conserved protein within the Microviridae, whose canonical members are X174, G4, and ␣3. However, despite 70% homology on the amino acid level, overexpression of a foreign Microviridae external scaffolding protein is a potent cross-species inhibitor of morphogenesis. Mutants that are resistant to the expression of a foreign scaffolding protein cannot be obtained via one mutational step. To define the requirements for and constraints on scaffolding protein interactions, chimeric external scaffolding proteins have been constructed and analyzed for effects on in vivo assembly. The results of these experiments suggest that at least two cross-species inhibitory domains exist within these proteins; one domain most likely blocks procapsid formation, and the other allows procapsid assembly but blocks DNA packaging. A mutation conferring resistance to the expression of a chimeric protein (chiD r ) that inhibits DNA packaging was isolated. The mutation maps to gene A, which encodes a protein essential for packaging. The chiD r mutation confers resistance only to a chimeric D protein; the mutant is still inhibited by the expression of foreign D proteins.The results presented here demonstrate how closely related proteins could be developed into antiviral agents that specifically target virion morphogenesis.The proper assembly of viral proteins and nucleic acids into a biologically active virion involves numerous and diverse macromolecular interactions. While structural proteins must correctly interact with other structural proteins, proper morphogenesis is equally dependent on interactions between structural and scaffolding proteins. Viral scaffolding proteins are transiently associated with morphogenetic intermediates but are not found in the mature viral particle (10,12,17,22). These proteins promote the efficiency and fidelity of particle formation by ensuring proper interactions between viral proteins, promoting the nucleation of assembly, and aiding in the formation of a precisely sized capsid (13,16,19). In the Microviridae, assembly is dependent on two scaffolding proteins, an internal and an external species. The assembly pathway has been extensively characterized (8), and the atomic structures of both the X174 virion and a morphogenetic intermediate containing a full complement of scaffolding proteins have been solved (2,3,14,15). Therefore, the results of genetic and biochemical analyses can be interpreted within a structural context.The Microviridae assembly pathway is illustrated in Fig. 1. The first detectable morphogenetic intermediates are the 9S and 6S particles, res...

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Nucleotide sequence of the genome of the bacteriophage α3: interrelationship of the genome structure and the gene products with those of the phages, θX174, G4 and θK

Cited by 31 publications

References 31 publications

Molecular Characterization of a Bacteriophage (Chp2) from Chlamydia psittaci

Molecular Characterization of a Bacteriophage (Chp2) from Chlamydia psittaci

Microviridae , a Family Divided: Isolation, Characterization, and Genome Sequence of φMH2K, a Bacteriophage of the Obligate Intracellular Parasitic Bacterium Bdellovibrio bacteriovorus

Foreign and Chimeric External Scaffolding Proteins as Inhibitors of Microviridae Morphogenesis

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