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Structural investigation of a premature filamentous bateriophage virus by solid-state NMR

Filamentous bacteriophages are viruses that infect bacteria. Prior to assembly, the non-structural gene V protein (gVp), one of the 10 genes of filamentous phage, binds to a phage-replicated DNA during the rolling circle replication process thereby, isolating a single-stranded (ss) DNA via the formation of a protein-ssDNA complex. Understanding the structure of this premature virus is a key element in unraveling phage assembly. Although X-ray and NMR structures of gVp are known, a high-resolution structure of the complex is yet to be established.

Here, we present a magic-angle spinning solid-state NMR study of an in vitro complex of a ssDNA molecule isolated from fd phage with the fd-gVp protein. Analysis of multi-dimensional experiments on labeled complexes provided, close-to-complete chemical shift assignment, which provides the overall secondary structure of the protein in the complex, and qualitative information on protein mobility. Further chemical shift analysis allows comparison to existing isolated gVp structures, and suggests that its structure in the complex differs from existing structures in solution and as a crystal.