title: Preferential binding of fd gene 5 protein to tetraplex nucleic acid structures.
abstract: The gene 5 protein of filamentous bacteriophage fd is a single-stranded DNA-binding protein that binds non-specifically to all single-stranded nucleic acid sequences, but in addition is capable of specific binding to the sequence d(GT(5)G(4)CT(4)C) and the RNA equivalent r(GU(5)G(4)CU(4)C), the latter interaction being important for translational repression. We show that this sequence preference arises from the formation of a tetraplex structure held together by a central block of G-quartets, the structure of which persists in the complex with gene 5 protein. Binding of gene 5 protein to the tetraplex leads to formation of a approximately 170 kDa nucleoprotein complex consisting of four oligonucleotide strands and eight gene 5 protein dimers, with a radius of gyration of 45 A and an overall maximum dimension of 120-130 A. A model of the complex is presented that is consistent with the data obtained. It is proposed that the G-quartet may act as a nucleation site for binding gene 5 protein to adjacent single-stranded regions, suggesting a novel mechanism for translational repression.
authors.affiliation: Biophysics Laboratories Institute of Biomedical and Biomolecular Science, University of Portsmouth, St Michael's Building, White Swan Road, Portsmouth, PO1 2DT, UK.
authors.forename: A W
authors.initials: AW
authors.lastname: Oliver
authors.forename: I
authors.initials: I
authors.lastname: Bogdarina
authors.forename: E
authors.initials: E
authors.lastname: Schroeder
authors.forename: I A
authors.initials: IA
authors.lastname: Taylor
authors.forename: G G
authors.initials: GG
authors.lastname: Kneale
mesh_terms: D002850:Chromatography, Gel; D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000821:virology; D054856:G-Quadruplexes; D015967:Gene Expression Regulation, Viral; D006147:Guanine / Q000737:chemistry; D017912:Inovirus / Q000737:chemistry* / Q000378:metabolism*; D008027:Light; D008954:Models, Biological; D009841:Oligonucleotides / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012542:Scattering, Radiation; D014461:Ultracentrifugation; D014466:Ultraviolet Rays; D014764:Viral Proteins / Q000378:metabolism*; D014965:X-Rays
chemical_list: D004268:DNA-Binding Proteins; D009841:Oligonucleotides; D014764:Viral Proteins; C068293:gene 5 protein, Enterobacteria phage T4; D006147:Guanine; D004247:DNA