Ring Separation Highlights the Protein-Folding Mechanism Used by the Phage EL-Encoded Chaperonin.

Chaperonins are ubiquitous, ATP-dependent protein-folding molecular machines that are essential for all forms of life. Bacteriophage φEL encodes its own chaperonin to presumably fold exceedingly large viral proteins via profoundly different nucleotide-binding conformations. Our structural investigations indicate that ATP likely binds to both rings simultaneously and that a misfolded substrate acts as the trigger for ATP hydrolysis.

Complete Genome Sequence of the Novel Giant Pseudomonas Phage PaBG.

The novel giant Pseudomonas aeruginosa bacteriophage PaBG was isolated from a water sample of the ultrafreshwater Lake Baikal. We report the complete genome sequence of this Myoviridae bacteriophage, comprising 258,139 bp of double-stranded DNA containing 308 predicted open reading frames.

Enzymatic characterization of a lysin encoded by bacteriophage EL.

The bacteriophage EL is a virus that specifically attacks the human pathogen . This phage carries a large genome that encodes for its own chaperonin which presumably facilitates the proper folding of phage proteins independently of the host chaperonin system. EL also encodes a lysin enzyme, a critical component of the lytic cycle that is responsible for digesting the peptidoglycan layer of the host cell wall.

Expression and functional characterization of the first bacteriophage-encoded chaperonin.

Chaperonins promote protein folding in vivo and are ubiquitously found in bacteria, archaea, and eukaryotes. The first viral chaperonin GroEL ortholog, gene product 146 (gp146), whose gene was earlier identified in the genome of bacteriophage EL, has been shown to be synthesized during phage propagation in Pseudomonas aeruginosa cells. The recombinant gp146 has been expressed in Escherichia coli and characterized by different physicochemical methods for the first time.

Structural conservation of the myoviridae phage tail sheath protein fold.

Bacteriophage phiKZ is a giant phage that infects Pseudomonas aeruginosa, a human pathogen. The phiKZ virion consists of a 1450 Å diameter icosahedral head and a 2000 Å-long contractile tail. The structure of the whole virus was previously reported, showing that its tail organization in the extended state is similar to the well-studied Myovirus bacteriophage T4 tail.

Characterization of tail sheath protein of giant bacteriophage phiKZ Pseudomonas aeruginosa.

The tail sheath protein of giant bacteriophage phiKZ Pseudomonas aeruginosa encoded by gene 29 was identified and its expression system was developed. Localization of the protein on the virion was confirmed by immunoelectron microscopy. Properties of gene product (gp) 29 were studied by electron microscopy, immunoblotting and limited trypsinolysis.

Identification and comparative analysis of the structural proteomes of phiKZ and EL, two giant Pseudomonas aeruginosa bacteriophages.

Giant bacteriophages phiKZ and EL of Pseudomonas aeruginosa contain 62 and 64 structural proteins, respectively, identified by ESI-MS/MS on total virion particle proteins. These identifications verify gene predictions and delineate the genomic regions dedicated to phage assembly and capsid formation (30 proteins were identified from a tailless phiKZ mutant). These data form the basis for future structural studies and provide insights into the relatedness of these large phages.

The structure of gene product 6 of bacteriophage T4, the hinge-pin of the baseplate.

The baseplate of bacteriophage T4 is a multicomponent protein complex, which controls phage attachment to the host. It assembles from six wedges and a central hub. During infection the baseplate undergoes a large conformational change from a dome-shaped to a flat, star-shaped structure.

The tail sheath structure of bacteriophage T4: a molecular machine for infecting bacteria.

The contractile tail of bacteriophage T4 is a molecular machine that facilitates very high viral infection efficiency. Its major component is a tail sheath, which contracts during infection to less than half of its initial length. The sheath consists of 138 copies of the tail sheath protein, gene product (gp) 18, which surrounds the central non-contractile tail tube.

Structure of the bacteriophage phi KZ lytic transglycosylase gp144.

Lytic transglycosylases are enzymes that act on the peptidoglycan of bacterial cell walls. They cleave the glycosidic linkage between N-acetylmuramoyl and N-acetylglucosaminyl residues with the concomitant formation of a 1,6-anhydromuramoyl product. The x-ray structure of the lytic transglycosylase gp144 from the Pseudomonas bacteriophage phi KZ has been determined to 2.

Cryo-EM study of the Pseudomonas bacteriophage phiKZ.

The phiKZ virus is one of the largest known bacteriophages. It infects Pseudomonas aeruginosa, which is frequently pathogenic in humans, and, therefore, has potential for phage therapy. The phiKZ virion consists of an approximately 1450 A diameter icosahedral head and an approximately 2000 A long contractile tail.

From structure of the complex to understanding of the biology.

The most extensive structural information on viruses relates to apparently icosahedral virions and is based on X-ray crystallography and on cryo-electron microscopy (cryo-EM) single-particle reconstructions. Both techniques lean heavily on imposing icosahedral symmetry, thereby obscuring any deviation from the assumed symmetry. However, tailed bacteriophages have icosahedral or prolate icosahedral heads that have one obvious unique vertex where the genome can enter for DNA packaging and exit when infecting a host cell.

Evolution of bacteriophage tails: Structure of T4 gene product 10.

The success of tailed bacteriophages to infect cells far exceeds that of most other viruses on account of their specialized tail and associated baseplate structures. The baseplate protein gene product (gp) 10 of bacteriophage T4, whose structure was determined to 1.2 A resolution, was fitted into the cryo-electron microscopy structures of the pre and post-infection conformations of the virus.

Structure, stability, and biological activity of bacteriophage T4 gene product 9 probed with mutagenesis and monoclonal antibodies.

Gene product (gp) 9 connects the long tail fibers and triggers the structural transition of T4 phage baseplate at the beginning of infection process. Gp9 is a parallel homotrimer with 288 amino acid residues per chain that forms three domains. To investigate the role of the gp9 amino terminus, we have engineered a set of mutants with deletions and random substitutions in this part.

The structural proteome of Pseudomonas aeruginosa bacteriophage phiKMV.

The structural proteome of phiKMV, a lytic bacteriophage infecting Pseudomonas aeruginosa, was analysed using two approaches. In one approach, structural proteins of the phage were fractionated by SDS-PAGE for identification by liquid chromatography-mass spectrometry (LC-MS). In a second approach, a whole-phage shotgun analysis (WSA) was applied.

The tail structure of bacteriophage T4 and its mechanism of contraction.

Bacteriophage T4 and related viruses have a contractile tail that serves as an efficient mechanical device for infecting bacteria. A three-dimensional cryo-EM reconstruction of the mature T4 tail assembly at 15-A resolution shows the hexagonal dome-shaped baseplate, the extended contractile sheath, the long tail fibers attached to the baseplate and the collar formed by six whiskers that interact with the long tail fibers. Comparison with the structure of the contracted tail shows that tail contraction is associated with a substantial rearrangement of the domains within the sheath protein and results in shortening of the sheath to about one-third of its original length.

A three-dimensional cryo-electron microscopy structure of the bacteriophage phiKZ head.

The three-dimensional structure of the Pseudomonas aeruginosa bacteriophage phiKZ head has been determined by cryo-electron microscopy and image reconstruction to 18A resolution. The head has icosahedral symmetry measuring 1455 A in diameter along 5-fold axes and a unique portal vertex to which is attached an approximately 1800 A-long contractile tail. The 65 kDa major capsid protein, gp120, is organized into a surface lattice of hexamers, with T = 27 triangulation.

Structural and functional similarities between the capsid proteins of bacteriophages T4 and HK97 point to a common ancestry.

Gene product (gp) 24 of bacteriophage T4 forms the pentameric vertices of the capsid. Using x-ray crystallography, we found the principal domain of gp24 to have a polypeptide fold similar to that of the HK97 phage capsid protein plus an additional insertion domain. Fitting gp24 monomers into a cryo-EM density map of the mature T4 capsid suggests that the insertion domain interacts with a neighboring subunit, effecting a stabilization analogous to the covalent crosslinking in the HK97 capsid.

Three-dimensional rearrangement of proteins in the tail of bacteriophage T4 on infection of its host.

The contractile tail of bacteriophage T4 undergoes major structural transitions when the virus attaches to the host cell surface. The baseplate at the distal end of the tail changes from a hexagonal to a star shape. This causes the sheath around the tail tube to contract and the tail tube to protrude from the baseplate and pierce the outer cell membrane and the cell wall before reaching the inner cell membrane for subsequent viral DNA injection.

The bacteriophage T4 DNA injection machine.

The tail of bacteriophage T4 consists of a contractile sheath surrounding a rigid tube and terminating in a multiprotein baseplate, to which the long and short tail fibers of the phage are attached. Upon binding of the fibers to their cell receptors, the baseplate undergoes a large conformational switch, which initiates sheath contraction and culminates in transfer of the phage DNA from the capsid into the host cell through the tail tube. The baseplate has a dome-shaped sixfold-symmetric structure, which is stabilized by a garland of six short tail fibers, running around the periphery of the dome.

Molecular architecture of the prolate head of bacteriophage T4.

The head of bacteriophage T4 is a prolate icosahedron with one unique portal vertex to which the phage tail is attached. The three-dimensional structure of mature bacteriophage T4 head has been determined to 22-A resolution by using cryo-electron microscopy. The T4 capsid has a hexagonal surface lattice characterized by the triangulation numbers T(end) = 13 laevo for the icosahedral caps and T(mid) = 20 for the midsection.

Three-dimensional structure of bacteriophage T4 baseplate.

The baseplate of bacteriophage T4 is a multiprotein molecular machine that controls host cell recognition, attachment, tail sheath contraction and viral DNA ejection. We report here the three-dimensional structure of the baseplate-tail tube complex determined to a resolution of 12 A by cryoelectron microscopy. The baseplate has a six-fold symmetric, dome-like structure approximately 520 A in diameter and approximately 270 A long, assembled around a central hub.

The genome of bacteriophage phiKMV, a T7-like virus infecting Pseudomonas aeruginosa.

The complete DNA sequence of a new lytic T7-like bacteriophage phiKMV is presented. It is the first genome sequence of a member of the Podoviridae that infects Pseudomonas aeruginosa. The linear G + C-rich (62.

Structure and location of gene product 8 in the bacteriophage T4 baseplate.

Many bacteriophages, such as T4, T7, RB49, and phi29, have complex, sometimes multilayered, tails that facilitate an almost 100% success rate for the viral particles to infect host cells. In bacteriophage T4, there is a baseplate, which is a multiprotein assembly, at the distal end of the contractile tail. The baseplate communicates to the tail that the phage fibers have attached to the host cell, thereby initiating the infection process.