title: Domain rearrangement of SRP protein Ffh upon binding 4.5S RNA and the SRP receptor FtsY.
abstract: The signal recognition particle (SRP) mediates membrane targeting of translating ribosomes displaying a signal-anchor sequence. In Escherichia coli, SRP consists of 4.5S RNA and a protein, Ffh, that recognizes the signal peptide emerging from the ribosome and the SRP receptor at the membrane, FtsY. In the present work, we studied the interactions between the NG and M domains in Ffh and their rearrangements upon complex formation with 4.5S RNA and/or FtsY. In free Ffh, the NG and M domains are facing one another in an orientation that allows cross-linking between positions 231 in the G domain and 377 in the M domain. There are binding interactions between the two domains, as the isolated domains form a strong complex. The interdomain contacts are disrupted upon binding of Ffh to 4.5S RNA, consuming a part of the total binding energy of 4.5S RNA-Ffh association that is roughly equivalent to the free energy of domain binding to each other. In the SRP particle, the NG domain binds to 4.5S RNA in a region adjacent to the binding site of the M domain. Ffh binding to FtsY also requires a reorientation of NG and M domains. These results suggest that in free Ffh, the binding sites for 4.5S RNA and FtsY are occluded by strong domain-domain interactions which must be disrupted for the formation of SRP or the Ffh-FtsY complex.
authors.affiliation: Institute of Molecular Biology, University of Witten/Herdecke, Germany.
authors.forename: Iwona
authors.initials: I
authors.lastname: Buskiewicz
authors.forename: Andriy
authors.initials: A
authors.lastname: Kubarenko
authors.forename: Frank
authors.initials: F
authors.lastname: Peske
authors.forename: Marina V
authors.initials: MV
authors.lastname: Rodnina
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wintermeyer
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012329:RNA, Bacterial; D012335:RNA, Ribosomal / Q000737:chemistry* / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000378:metabolism; D018271:Signal Recognition Particle / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C409968:4.5S RNA; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; C087406:FtsY protein, Bacteria; D012329:RNA, Bacterial; D012335:RNA, Ribosomal; D018160:Receptors, Cytoplasmic and Nuclear; D018271:Signal Recognition Particle