NMR Studies of the Structure and Dynamics of Membrane-Bound Bacteriophage Pf1 Coat Protein

Filamentous bacteriophage coat protein undergoes a remarkable structural transition during the viral assembly process as it is transferred from the membrane environment of the cell, where it spans the phospholipid bilayer, to the newly extruded virus particles. Nuclear magnetic resonance (NMR) studies show the membrane-bound form of the 46-residue Pf1 coat protein to be surprisingly complex with five distinct regions. The secondary structure consists of a long hydrophobic helix (residues 19 to 42) that spans the bilayer and a short amphipathic helix (residues 6 to 13) parallel to the plane of the bilayer. The NH$_2$-terminus (residues 1 to 5), the COOH-terminus (residues 43 to 46), and residues 14 to 18 connecting the two helices are mobile. By comparing the structure and dynamics of the membrane-bound coat protein with that of the viral form as determined by NMR and neutron diffraction, essential features of assembly process can be identified.