ORIENTATIONS OF TYROSINE-21 AND TYROSINE-24 IN COAT SUBUNITS OF FF FILAMENTOUS VIRUS - DETERMINATION BY RAMAN LINEAR INTENSITY DIFFERENCE SPECTROSCOPY AND IMPLICATIONS FOR SUBUNIT PACKING
M. Matsuno et al., ORIENTATIONS OF TYROSINE-21 AND TYROSINE-24 IN COAT SUBUNITS OF FF FILAMENTOUS VIRUS - DETERMINATION BY RAMAN LINEAR INTENSITY DIFFERENCE SPECTROSCOPY AND IMPLICATIONS FOR SUBUNIT PACKING, Biophysical journal, 74(6), 1998, pp. 3217-3225
Virions of the Ff group of bacteriophages (fd, fl, M13) are morphologi
cally identical filaments (similar to 6-nm diameter x similar to 880-n
m length) in which a covalently closed, single-stranded DNA genome is
sheathed by similar to 2700 copies of a 50-residue alpha-helical subun
it (pVIII). Orientations of pVIII tyrosines (Tyr(21) and Tyr(24)) with
respect to the filament axis have been determined by Raman linear int
ensity difference (RLID) spectroscopy of flow-oriented mutant virions
in which the tyrosines were independently mutated to methionine. The r
esults show that the twofold axis of the phenolic ring (C1-C4 line) of
Tyr(21) is inclined at 39.5 +/- 1.4 degrees from the virion axis, and
that of Tyr(24) is inclined at 43.7 +/- 0.6 degrees. The orientation
determined for the Tyr(21) phenol ring is close to that of a structura
l model previously proposed on the basis of fiber x-ray diffraction re
sults (Protein Data Bank, identification code 1IFJ). On the other hand
, the orientation determined for the Tyr(24) phenol ring differs from
the diffraction-based model by a 40 degrees rotation about the C alpha
-C beta bond. The RLID results also indicate that each tyrosine mutati
on does not greatly affect the orientation of either the remaining tyr
osine or single tryptophan (Trp(26)) of pVIII. On the basis of these r
esults, a refined model is proposed for the coat protein structure in
Ff.