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PubMed2004

Phospholipid molecular species profiles of tectiviruses infecting Gram-negative and Gram-positive hosts.

The phospholipid (PL) molecular species compositions of bacteriophages PRD1 and Bam35 as well as their respective hosts were determined quantitatively using liquid chromatography/electrospray ionization mass-spectrometry (LC-ESI-MS) and backed up by gas-chromatographic/mass-spectrometric (GC-MS) analysis of the total fatty acids (FAs). The results showed that both viruses contain significantly more phosphatidylglycerol (PG) and less phosphatidylethanolamine (PE) than the host membranes. Only modest differences in the molecular species composition of the viruses and their respective hosts were observed, indicating that the virus assembly process is relatively nonselective in respect of the fatty acid (FA) proportion of phospholipids (PL). These data indicate that the PL composition of these two viruses is largely, albeit not exclusively, determined by the availability of phospholipids in the host membrane.

Bacillus Phages↗
PubMed1999

Viral evolution revealed by bacteriophage PRD1 and human adenovirus coat protein structures.

The unusual bacteriophage PRD1 features a membrane beneath its icosahedral protein coat. The crystal structure of the major coat protein, P3, at 1.85 A resolution reveals a molecule with three interlocking subunits, each with two eight-stranded viral jelly rolls normal to the viral capsid, and putative membrane-interacting regions. Surprisingly, the P3 molecule closely resembles hexon, the equivalent protein in human adenovirus. Both viruses also have similar overall architecture, with identical capsid lattices and attachment proteins at their vertices. Although these two dsDNA viruses infect hosts from very different kingdoms, their striking similarities, from major coat protein through capsid architecture, strongly suggest their evolutionary relationship.

Adenoviruses, Human↗
PubMed2003

Bacteriophage observations and evolution.

Bacteriophages are classified into one order and 13 families. Over 5100 phages have been examined in the electron microscope since 1959. At least 4950 phages (96%) are tailed. They constitute the order Caudovirales and three families. Siphoviridae or phages with long, noncontractile tails predominate (61% of tailed phages). Polyhedral, filamentous, and pleomorphic phages comprise less than 4% of bacterial viruses. Bacteriophages occur in over 140 bacterial or archaeal genera. Their distribution reflects their origin and bacterial phylogeny. Bacteriophages are polyphyletic, arose repeatedly in different hosts, and constitute 11 lines of descent. Tailed phages appear as monophyletic and as the oldest known virus group.

Bacteriophages↗
PubMed2000

Assembly of bacteriophage PRD1 spike complex: role of the multidomain protein P5.

The spike structure of bacteriophage PRD1 is comprised of proteins P2, P5, and P31. It resembles the corresponding receptor-binding structure of adenoviruses. We show that purified recombinant protein P5 is an elongated (30 x 2.7 nm; R(h) = 5.5 nm), multidomain trimer which can slowly associate into nonamers. Cleavage of the 340 amino acid long P5 with collagenase yields 2 fragments. The larger, 205 amino acid long C-terminal fragment appears to contain the residues responsible for the trimerization of the protein, whereas the smaller N-terminal part mediates the interaction of P5 with the pentameric vertex protein P31 (24 x 2.5 nm, R(h) = 4.2 nm). In addition, the presence of the N-terminal sequence is required for the formation of the P5 nonamer. The results presented here suggest that P5 and P31 form an elongated adaptor complex at the 5-fold vertexes of the virion which anchors the adsorption protein P2 (21 x 2.5 nm; R(h) = 4.1 nm). Our results also suggest that the P5 trimer forms a substantial part of the viral spike shaft that was previously thought to be composed exclusively of protein P2.

Amino Acid Motifs↗
PubMed2000

Bacteriophage PRD1 DNA entry uses a viral membrane-associated transglycosylase activity.

Amino acid sequence analyses have indicated that the amino-terminal part of bacteriophage PRD1 structural protein P7 carries a conserved transglycosylase domain. We analysed wild-type PRD1 and different mutant particles in zymograms and found a glycolytic activity that was associated with protein P7. This is the first time a putative bacteriophage or plasmid lytic transglycosylase has been shown to have an enzymatic activity. In the absence of protein P7, the phage DNA replication and host cell lysis were delayed. Gene VII of PRD1 is known to encode proteins P7 and P14. In this investigation, the open reading frame coding for P14 was mapped to the 3' end of gene VII. Proteins P7 and P14 probably form a heteromultimeric complex, which is located at the particle vertices and is involved in the early steps of the PRD1 life cycle

Cell Membrane↗
PubMed2004

Bacteriophages that infect the cellulolytic ruminal bacterium Ruminococcus albus AR67.

AIM: To isolate bacterial viruses that infect the ruminal cellulolytic bacterium Ruminococcus albus. METHODS: Four phages infecting R. albus AR67 were isolated under anaerobic conditions using the soft-agar overlay technique. The phages were characterized on morphology, solvent stability, nucleic acid type and digestion characteristics. Two phages, phiRa02 and phiRa04 comprised icosahedral virions with linear double-stranded DNA and appeared to belong to the family Podoviridae [corrected] The other two phages are most likely filamentous phages with circular single-stranded DNA of the family Inoviridae. SIGNIFICANCE OF THE STUDY: Viruses of the family Inoviridae [corrected] have not previously been isolated from rumen bacteria. The phages isolated in this study are the first phages shown to infect the cellulolytic bacteria of the rumen. This suggests that the cellulolytic populations of the rumen are subject to lytic events that may impact on the ability of these bacteria to degrade plant fibre and on the nutrition of the animal.

Anaerobiosis↗
PubMed1997

The IncP plasmid-encoded cell envelope-associated DNA transfer complex increases cell permeability.

IncP-type plasmids are broad-host-range conjugative plasmids. DNA translocation requires DNA transfer-replication functions and additional factors required for mating pair formation (Mpf). The Mpf system is located in the cell membranes and is responsible for DNA transport from the donor to the recipient. The Mpf complex acts as a receptor for IncP-specific phages such as PRD1. In this investigation, we quantify the Mpf complexes on the cell surface by a phage receptor saturation technique. Electrochemical measurements are used to show that the Mpf complex increases cell envelope permeability to lipophilic compounds and ATP. In addition it reduces the ability of the cells to accumulate K+. However, the Mpf complex does not dissipate the membrane voltage. The Mpf complex is rapidly disassembled when intracellular ATP concentration is decreased, as measured by a PRD1 adsorption assay.

Adenosine Triphosphate↗
PubMed1997

Changes in host cell energetics in response to bacteriophage PRD1 DNA entry.

Double-stranded DNA bacteriophage PRD1 infects a variety of gram-negative bacteria harboring an IncP-type conjugative plasmid. The plasmid codes for the DNA transfer phage receptor complex in the cell envelope. Our goal was, by using a collection of mutant phage particles for which the variables are the DNA content and/or the presence of the receptor-binding protein, to obtain information on the energy requirements for DNA entry as well as on alterations in the cellular energetics taking place during the first stages of infection. We studied the fluxes of tetraphenylphosphonium (TPP+), phenyldicarbaundecaborane (PCB-), and K+ ions as well as ATP through the envelope of Salmonella typhimurium cells. The final level of the membrane voltage (delta psi) indicator TPP+ accumulated by the infected cells exceeds the initial level before the infection. Besides the effects on TPP+ accumulation, PRD1 induces the leakage of ATP and K+ from the cytosol. All these events were induced only by DNA-containing infectious particles and were cellular ATP and delta psi dependent. PRD1-caused changes in delta psi and in PCB- binding differ considerably from those observed in other bacteriophage infections studied. These results are in accordance with the presence of a specific channel engaged in phage PRD1 DNA transport.

Adenosine Triphosphate↗
PubMed2000

A new mutant class, made by targeted mutagenesis, of phage PRD1 reveals that protein P5 connects the receptor binding protein to the vertex.

Phage PRD1 and adenovirus share a number of structural and functional similarities, one of which is the vertex organization at the fivefold-symmetry positions. We developed an in vitro mutagenesis system for the linear PRD1 genome in order to make targeted mutations. The role of protein P5 in the vertex structure was examined by this method. Mutation in gene V revealed that protein P5 is essential. The absence of P5 did not compromise the particle assembly or DNA packaging but led to a deficient vertex structure where the receptor binding protein P2, in addition to protein P5, was missing. P5(-) particles also lost their DNA upon purification. Based on this and previously published information we propose a spatial model for the spike structure at the vertices. This resembles to the corresponding structure in adenovirus.

Adsorption↗