SUBUNIT ORIENTATION IN THE FILAMENTOUS VIRUS FF(FD, F1, M13)

The Ff filamentous viruses (fd, M13, f1) are important models for memb rane protein assembly and are used extensively as cloning vectors and vehicles for peptide display The thread-like virion (approximate to 6 nm x 880 nm) comprises a single-stranded DNA genome sheathed by approx imate to 2700 copies of a 50-residue alpha-helical subunit (pVIII). Th e average inclination of pVIII subunits from the virion axis has been determined experimentally by polarized Raman microspectroscopy of orie nted fd fibers, using the amide I Raman tensors obtained from a peptid e single crystal. It is found that the average tilt angle, theta, betw een the pVIII alpha-helix and the virion axis falls within the range 1 3 < theta < 20 degrees. (C) 1996 Academic Press Limited