Structure of the coat protein in Pf1 bacteriophage determined by solid-state NMR Spectroscopy

The atomic resolution structure of Pf1 coat protein determined by solid-state NMR spectroscopy of magnetically aligned filamentous bacteriophage particles in solution is compared to the structures previously determined by X-ray fiber and neutron diffraction, the structure of its membrane-bound form, and the structure of fd coat protein. These structural comparisons provide insights into several biological properties, differences between class I and class II filamentous bacteriophages, and the assembly process. The six N-terminal amino acid residues adopt an unusual double hook conformation on the outside of the bacteriophage particle. The solid-state NMR results indicate that at 30 degreesC, some of the coat protein subunits assume a single, fully structured conformation, and some have a few mobile residues that provide a break between two helical segments, in agreement with structural models from X-ray fiber and neutron diffraction, respectively. The atomic resolution structure determined by solid-state NMR for residues 7-14 and 18-46, which excludes the N-terminal double hook and the break between the helical segments, but encompasses more than 80% of the backbone including the distinct kink at residue 29, agrees with that determined by X-ray fiber diffraction with an RMSD value of 2.0 Angstrom. The symmetry and distance constraints determined by X-ray fiber and neutron diffraction enable the construction of an accurate model of the bacteriophage particle from the coordinates of the coat protein monomers. (C) 2004 Elsevier Ltd. All rights reserved.