title: Formation of SRP-like particle induces a conformational change in E. coli 4.5S RNA.
abstract: E. coli P48 protein is homologous to the SRP54 component of the eukaryotic signal recognition particle. In vivo, P48 is associated with 4.5S RNA which shares a homology with eukaryotic SRP RNA. To study the interaction between P48 and 4.5S RNA in vitro, we used 4.5S RNA with fluorescein coupled to the 3'-terminal ribose. Upon binding of P48, the fluorescent 4.5S RNA shows a substantial decrease in fluorescence. Fluorescence quenching as well as anisotropy measurements reveal that the effect is not due to a direct interaction of P48 with the dye. This suggests that the binding of P48 induces a conformational change in 4.5S RNA which affects the structure at the 3' end of the RNA. From equilibrium titrations with fluorescent 4.5S RNA, a dissociation constant of 0.15 microns is obtained for the RNA.protein complex. The formation of the complex is not affected by GTP binding to or hydrolysis by P48.
authors.affiliation: Institut für Molekularbiologie, Universität Witten/Herdecke, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Lentzen
authors.forename: B
authors.initials: B
authors.lastname: Dobberstein
authors.forename: W
authors.initials: W
authors.lastname: Wintermeyer
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D019793:Fluorescein; D005452:Fluoresceins; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000737:chemistry*; D018271:Signal Recognition Particle / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; D005452:Fluoresceins; D005456:Fluorescent Dyes; D012329:RNA, Bacterial; D018271:Signal Recognition Particle; D019793:Fluorescein