title: Charge-driven dynamics of nascent-chain movement through the SecYEG translocon.
abstract: On average, every fifth residue in secretory proteins carries either a positive or a negative charge. In a bacterium such as Escherichia coli, charged residues are exposed to an electric field as they transit through the inner membrane, and this should generate a fluctuating electric force on a translocating nascent chain. Here, we have used translational arrest peptides as in vivo force sensors to measure this electric force during cotranslational chain translocation through the SecYEG translocon. We find that charged residues experience a biphasic electric force as they move across the membrane, including an early component with a maximum when they are 47-49 residues away from the ribosomal P site, followed by a more slowly varying component. The early component is generated by the transmembrane electric potential, whereas the second may reflect interactions between charged residues and the periplasmic membrane surface.
authors.affiliation: Center for Biomembrane Research, Department of Biochemistry and Biophysics Stockholm University, Stockholm, Sweden.
authors.forename: Nurzian
authors.initials: N
authors.lastname: Ismail
authors.affiliation: Center for Biomembrane Research, Department of Biochemistry and Biophysics Stockholm University, Stockholm, Sweden.
authors.forename: Rickard
authors.initials: R
authors.lastname: Hedman
authors.affiliation: Center for Biomembrane Research, Department of Biochemistry and Biophysics Stockholm University, Stockholm, Sweden.|Dept. of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Lindén
authors.affiliation: Center for Biomembrane Research, Department of Biochemistry and Biophysics Stockholm University, Stockholm, Sweden.|Science for Life Laboratory Stockholm University, Solna, Sweden.
authors.forename: Gunnar
authors.initials: G
authors.lastname: von Heijne
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology*; D000069816:SEC Translocation Channels
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000069816:SEC Translocation Channels; C065493:SecE protein, E coli; C088616:SecG protein, E coli; C057841:SecY protein, E coli