title: Dynamic structure of the translocon SecYEG in membrane: direct single molecule observations.
abstract: Purified SecYEG was reconstituted into liposomes and studied in near-native conditions using atomic force microscopy. These SecYEG proteoliposomes were active in translocation assays. Changes in the structure of SecYEG as a function of time were directly visualized. The dynamics observed were significant in magnitude (∼1-10 Å) and were attributed to the two large loops of SecY linking transmembrane helices 6-7 and 8-9. In addition, we identified a distribution between monomers and dimers of SecYEG as well as a smaller population of higher order oligomers. This work provides a new vista of the flexible and dynamic structure of SecYEG, an intricate and vital membrane protein.
authors.affiliation: Departments of Physics and Astronomy, Columbia, Missouri 65211.
authors.forename: Raghavendar Reddy
authors.initials: RR
authors.lastname: Sanganna Gari
authors.affiliation: Departments of Physics and Astronomy, Columbia, Missouri 65211.
authors.forename: Nathan C
authors.initials: NC
authors.lastname: Frey
authors.affiliation: Biochemistry, University of Missouri, Columbia, Missouri 65211.
authors.forename: Chunfeng
authors.initials: C
authors.lastname: Mao
authors.affiliation: Biochemistry, University of Missouri, Columbia, Missouri 65211.
authors.forename: Linda L
authors.initials: LL
authors.lastname: Randall
authors.affiliation: Departments of Physics and Astronomy, Columbia, Missouri 65211; Biochemistry, University of Missouri, Columbia, Missouri 65211. Electronic address: kinggm@missouri.edu.
authors.forename: Gavin M
authors.initials: GM
authors.lastname: King
mesh_terms: D001693:Biological Transport, Active; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018625:Microscopy, Atomic Force; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020836:Protein Structure, Quaternary; D000069816:SEC Translocation Channels
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D000069816:SEC Translocation Channels; C065493:SecE protein, E coli; C088616:SecG protein, E coli; C057841:SecY protein, E coli
keywords: Atomic Force Microscopy; Membrane Biophysics; Membrane Proteins; Protein Conformation; Protein Dynamics; Protein Export; Secretion; Structural Biology