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Charge-driven dynamics of nascent-chain movement through the SecYEG translocon.

Authors
  • Ismail, Nurzian1
  • Hedman, Rickard1
  • Lindén, Martin1, 2
  • von Heijne, Gunnar1, 3
  • 1 Center for Biomembrane Research, Department of Biochemistry and Biophysics Stockholm University, Stockholm, Sweden. , (Sweden)
  • 2 Dept. of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden. , (Sweden)
  • 3 Science for Life Laboratory Stockholm University, Solna, Sweden. , (Sweden)
Type
Published Article
Journal
Nature Structural & Molecular Biology
Publisher
Springer Nature
Publication Date
Feb 01, 2015
Volume
22
Issue
2
Pages
145–149
Identifiers
DOI: 10.1038/nsmb.2940
PMID: 25558985
Source
Medline
License
Unknown

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.

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