A role for the two-helix finger of the SecA ATPase in protein translocation

Karl J. Erlandson, Stephanie B M Miller, Yunsun Nam, Andrew R. Osborne, Jochen Zimmer, Tom A. Rapoport

Research output: Contribution to journalArticle

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Abstract

An important step in the biosynthesis of many proteins is their partial or complete translocation across the plasma membrane in prokaryotes or the endoplasmic reticulum membrane in eukaryotes. In bacteria, secretory proteins are generally translocated after completion of their synthesis by the interaction of the cytoplasmic ATPase SecA and a protein-conducting channel formed by the SecY complex. How SecA moves substrates through the SecY channel is unclear. However, a recent structure of a SecA-SecY complex raises the possibility that the polypeptide chain is moved by a two-helix finger domain of SecA that is inserted into the cytoplasmic opening of the SecY channel. Here we have used disulphide-bridge crosslinking to show that the loop at the tip of the two-helix finger of Escherichia coli SecA interacts with a polypeptide chain right at the entrance into the SecY pore. Mutagenesis demonstrates that a tyrosine in the loop is particularly important for translocation, but can be replaced by some other bulky, hydrophobic residues. We propose that the two-helix finger of SecA moves a polypeptide chain into the SecY channel with the tyrosine providing the major contact with the substrate, a mechanism analogous to that suggested for hexameric, protein-translocating ATPases.

Original languageEnglish (US)
Pages (from-to)984-987
Number of pages4
JournalNature
Volume455
Issue number7215
DOIs
StatePublished - Oct 16 2008

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Protein Transport
Fingers
Adenosine Triphosphatases
Peptides
Tyrosine
Proteins
Protein Biosynthesis
Eukaryota
Mutagenesis
Endoplasmic Reticulum
Disulfides
Cell Membrane
Escherichia coli
Bacteria
Membranes

ASJC Scopus subject areas

  • General

Cite this

Erlandson, K. J., Miller, S. B. M., Nam, Y., Osborne, A. R., Zimmer, J., & Rapoport, T. A. (2008). A role for the two-helix finger of the SecA ATPase in protein translocation. Nature, 455(7215), 984-987. https://doi.org/10.1038/nature07439

A role for the two-helix finger of the SecA ATPase in protein translocation. / Erlandson, Karl J.; Miller, Stephanie B M; Nam, Yunsun; Osborne, Andrew R.; Zimmer, Jochen; Rapoport, Tom A.

In: Nature, Vol. 455, No. 7215, 16.10.2008, p. 984-987.

Research output: Contribution to journalArticle

Erlandson, KJ, Miller, SBM, Nam, Y, Osborne, AR, Zimmer, J & Rapoport, TA 2008, 'A role for the two-helix finger of the SecA ATPase in protein translocation', Nature, vol. 455, no. 7215, pp. 984-987. https://doi.org/10.1038/nature07439
Erlandson KJ, Miller SBM, Nam Y, Osborne AR, Zimmer J, Rapoport TA. A role for the two-helix finger of the SecA ATPase in protein translocation. Nature. 2008 Oct 16;455(7215):984-987. https://doi.org/10.1038/nature07439
Erlandson, Karl J. ; Miller, Stephanie B M ; Nam, Yunsun ; Osborne, Andrew R. ; Zimmer, Jochen ; Rapoport, Tom A. / A role for the two-helix finger of the SecA ATPase in protein translocation. In: Nature. 2008 ; Vol. 455, No. 7215. pp. 984-987.
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