title: Conformational studies of the C-terminal domain of bacteriophage Pf1 gene 5 protein.
abstract: The gene 5 protein (g5p) of the bacteriophage Pf1 is a 144 residue single-stranded (ss) DNA binding protein involved in replication and packaging of the viral DNA. Compared to the gene 5 proteins of other filamentous bacteriophages, such as fd, the Pf1 g5p has an additional C-terminal sequence ( approximately 40 residues) with an unusual amino acid composition, being particularly rich in proline, glutamine and alanine. This C-terminal sequence is susceptible to limited proteolysis, in contrast to the globular N-terminal domain of the protein. The C-terminal sequence has been shown to play a role in the stabilisation of the protein-ssDNA complex. In the present study, the DNA sequence corresponding to the 38 amino acid residue C-terminal peptide has been cloned and expressed. A variety of biophysical techniques suggest that this peptide has a largely irregular conformation in solution, in contrast to the N-terminal globular domain that is principally beta-sheet. However, circular dichroism (CD) spectroscopy indicates that the peptide can be induced to form a structure that resembles a left-handed polyproline-like (P(II)) helix, suggesting that the C-terminal tail of the protein may adopt a more structured conformation in the appropriate physiological environment.
authors.affiliation: Biophysics Laboratories, Institute of Biomedical and Biomolecular Science, University of Portsmouth, St Michael's Building, Portsmouth, UK.
authors.forename: D G
authors.initials: DG
authors.lastname: Fox
authors.forename: P D
authors.initials: PD
authors.lastname: Cary
authors.forename: G G
authors.initials: GG
authors.lastname: Kneale
mesh_terms: D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D002942:Circular Dichroism; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D015870:Gene Expression; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012997:Solvents; D013696:Temperature; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D004268:DNA-Binding Proteins; D012997:Solvents; D014764:Viral Proteins; C067863:gene 5 protein, Pseudomonas phage Pf1