Conformational Changes in Ff Phage Protein gVp upon Complexation with Its Viral Single-Stranded DNA Revealed Using Magic-Angle Spinning Solid-State NMR

Analysis of Pseudomonas aeruginosa Isolates from Patients with Cystic Fibrosis Revealed Novel Groups of Filamentous Bacteriophages

Pseudomonas aeruginosa is an opportunistic pathogen that can cause infections in humans, especially in hospital patients with compromised host defence mechanisms, including patients with cystic fibrosis. Filamentous bacteriophages represent a group of single-stranded DNA viruses infecting different bacteria, including P. aeruginosa and other human and animal pathogens; many of them can replicate when integrated into the bacterial chromosome. Filamentous bacteriophages can contribute to the virulence of P. aeruginosa and influence the course of the disease. There are just a few isolated and officially classified filamentous bacteriophages infecting P. aeruginosa, but genomic studies indicated the frequent occurrence of integrated prophages in many P. aeruginosa genomes. An analysis of sequenced genomes of P. aeruginosa isolated from upper respiratory tract (throat and nasal swabs) and sputum specimens collected from Russian patients with cystic fibrosis indicated a higher diversity of filamentous bacteriophages than first thought. A detailed analysis of predicted bacterial proteins revealed prophage regions representing the filamentous phages known to be quite distantly related to known phages. Genomic comparisons and phylogenetic studies enabled the proposal of several new taxonomic groups of filamentous bacteriophages.

Atomic-Resolution Structure of the Protein Encoded by Gene V of fd Bacteriophage in Complex with Viral ssDNA Determined by Magic-Angle Spinning Solid-State NMR

F-specific filamentous phages, elongated particles with circular single-stranded DNA encased in a symmetric protein capsid, undergo an intermediate step, where thousands of homodimers of a non-structural protein, gVp, bind to newly synthesized strands of DNA, preventing further DNA replication and preparing the circular genome in an elongated conformation for assembly of a new virion structure at the membrane. While the structure of the free homodimer is known, the ssDNA-bound conformation has yet to be determined. We report an atomic-resolution structure of the gVp monomer bound to ssDNA of fd phage in the nucleoprotein complex elucidated via magic-angle spinning solid-state NMR. The model presents significant conformational changes with respect to the free form. These modifications facilitate the binding mechanism and possibly promote cooperative binding in the assembly of the gVp-ssDNA complex.