Journal of the American Chemical Society, Vol.129, No.8, 2338-2344, 2007
Filamentous phage studied by magic-angle spinning NMR: Resonance assignment and secondary structure of the coat protein in Pf1
Assignments are presented for resonances in the magic-angle spinning solid-state NMR spectra of the major coat protein subunit of the filamentous bacteriophage Pf1. NMR spectra were collected on uniformly C-13 and N-15 isotopically enriched, polyethylene glycol precipitated samples of fully infectious and hydrated phage. Site-specific assignments were achieved for 231 of the 251 labeled atoms (92%) of the 46-residue-long coat protein, including 136 of the 138 backbone atoms, by means of two- and three-dimensional N-15 and C-13 correlation experiments. A single chemical shift was observed for the vast majority of atoms, suggesting a single conformation for the 7300 subunits in the 36 MDa virion in its high-temperature form. On the other hand, multiple chemical shifts were observed for the C alpha, C beta, and C gamma atoms of T5 in the helix terminus and the C alpha and C beta atoms of M42 in the DNA interaction domain. The chemical shifts of the backbone atoms indicate that the coat protein conformation involves a 40-residue continuous alpha-helix extending from residue 6 to the C-terminus.