Filamentous bacteriophages comprise a family of viruses that share a similar virion structure and life cycle. The virion is composed of a circular ssDNA wrapped by thousands of similar copies of a major coat protein and several different minor coat proteins in both ends. Due to the mass (tens of MegaDaltons) and dimensions (~7 nm in diameter, 600 – 2000 nm in length) of filamentous phages, structural models have been obtained primarily from fiber diffraction, and from static solid state NMR of aligned concentrated solutions. Yet, these models are incomplete, and vary even within individual virions. Also, some key questions regarding DNA structure, subunit-DNA interactions, microscopic polymorphism, and more, remain unclear or are in debate. Magic-angle spinning solid state NMR (MAS SSNMR) has been shown recently to be a complementary and successful method for studying the structure and dynamics of biological macromolecules. Examples are membrane proteins, protein aggregates and fibrils, and recently, the Pf1 filamentous phage. Also, sample preparation for MAS SSNMR is more flexible, and measurements can be performed in conditions, which are either biologically relevant, or important for their biophysical characterization. The goal of the proposed project is to structurally characterize and compare the three key phages fd, Ike, and Pf3, using MAS SSNMR as a principal spectroscopic tool. These phages were chosen, since they represent different structural properties of such virions. We anticipate that our proposed studies will resolve some of the key questions regarding the structural assembly of filamentous phages, and enhance our understanding on the possible ways in which these phages assemble at their host bacteria. Our results will also provide suitable model systems for studies of other complex biological systems.
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