Raman spectra have been measured of a nonapeptide which has an amino acid sequence identical to that of the C-terminal region of the major coat protein subunit of Filamentous bacteriophage Pf3. The peptide shows a strong tendency to form a β-sheet structure in aqueous solution. The β-sheet formation is significantly promoted by complexation with single-stranded DNA but not with double-stranded DNA. It is suggested that the C-terminal region of the Pf3 coat protein binds to the single-stranded DNA genome in the virion with a β-sheet conformation, in sharp contrast with the α-helical binding in other filamentous bacteriophages.
