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Title: The Chloroplast Tat Pathway Utilizes the Transmembrane Electric Potential as an Energy Source

Abstract

Here, the thylakoid membrane, located inside the chloroplast, requires proteins transported across it for plastid biogenesis and functional photosynthetic electron transport. The chloroplast Tat translocator found on thylakoids transports proteins from the plastid stroma to the thylakoid lumen. Previous studies have shown that the chloroplast Tat pathway is independent of NTP hydrolysis as an energy source and instead depends on the thylakoid transmembrane proton gradient to power protein translocation. Because of its localization on the same membrane as the proton motive force-dependent F0F1 ATPase, we believed that the chloroplast Tat pathway also made use of the thylakoid electric potential for transporting substrates. By adjusting the rate of photosynthetic proton pumping and by utilizing ionophores, we show that the chloroplast Tat pathway can also utilize the transmembrane electric potential for protein transport. Our findings indicate that the chloroplast Tat pathway is likely dependent on the total protonmotive force (PMF) as an energy source. As a protonmotive-dependent device, certain predictions can be made about structural features expected to be found in the Tat translocon, specifically, the presence of a proton well, a device in the membrane that converts electrical potential into chemical potential.

Authors:
 [1];  [1];  [1]
  1. Univ. of California, Davis, CA (United States). Dept. of Plant Biology
Publication Date:
Research Org.:
Univ. of California, Davis, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
OSTI Identifier:
1490449
Grant/Contract Number:  
FG02-03ER15405
Resource Type:
Accepted Manuscript
Journal Name:
Biophysical Journal
Additional Journal Information:
Journal Volume: 93; Journal Issue: 6; Journal ID: ISSN 0006-3495
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Braun, Nikolai A., Davis, Andrew W., and Theg, Steven M. The Chloroplast Tat Pathway Utilizes the Transmembrane Electric Potential as an Energy Source. United States: N. p., 2009. Web. doi:10.1529/biophysj.106.098731.
Braun, Nikolai A., Davis, Andrew W., & Theg, Steven M. The Chloroplast Tat Pathway Utilizes the Transmembrane Electric Potential as an Energy Source. United States. doi:10.1529/biophysj.106.098731.
Braun, Nikolai A., Davis, Andrew W., and Theg, Steven M. Tue . "The Chloroplast Tat Pathway Utilizes the Transmembrane Electric Potential as an Energy Source". United States. doi:10.1529/biophysj.106.098731. https://www.osti.gov/servlets/purl/1490449.
@article{osti_1490449,
title = {The Chloroplast Tat Pathway Utilizes the Transmembrane Electric Potential as an Energy Source},
author = {Braun, Nikolai A. and Davis, Andrew W. and Theg, Steven M.},
abstractNote = {Here, the thylakoid membrane, located inside the chloroplast, requires proteins transported across it for plastid biogenesis and functional photosynthetic electron transport. The chloroplast Tat translocator found on thylakoids transports proteins from the plastid stroma to the thylakoid lumen. Previous studies have shown that the chloroplast Tat pathway is independent of NTP hydrolysis as an energy source and instead depends on the thylakoid transmembrane proton gradient to power protein translocation. Because of its localization on the same membrane as the proton motive force-dependent F0F1 ATPase, we believed that the chloroplast Tat pathway also made use of the thylakoid electric potential for transporting substrates. By adjusting the rate of photosynthetic proton pumping and by utilizing ionophores, we show that the chloroplast Tat pathway can also utilize the transmembrane electric potential for protein transport. Our findings indicate that the chloroplast Tat pathway is likely dependent on the total protonmotive force (PMF) as an energy source. As a protonmotive-dependent device, certain predictions can be made about structural features expected to be found in the Tat translocon, specifically, the presence of a proton well, a device in the membrane that converts electrical potential into chemical potential.},
doi = {10.1529/biophysj.106.098731},
journal = {Biophysical Journal},
number = 6,
volume = 93,
place = {United States},
year = {2009},
month = {1}
}

Journal Article:
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Citation Metrics:
Cited by: 40 works
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Figures / Tables:

Figure 1 Figure 1: Valinomycin decreases the rate of cpTat transport at low values of ΔpH. (A) The import data of four ionophore treatments replicated nine times are shown, as well as triplicates of 10% substrate loading standards used for quantification purposes interspersed with a nonradioactive molecular weight marker (empty lanes). Themore » average percentage transport of each treatment as well as the standard errors and t-tests are presented graphically (B). The two pairs of columns labeled Control and Nigericin show the percentage transport of iOE17 Tat substrate under highlight conditions in the absence and presence of 300 nM of nigericin. Light shaded bars are untreated reactions, and solid bars are reactions that contain 1 μM valinomycin.« less

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Works referencing / citing this record:

Twin-arginine-dependent translocation of folded proteins
journal, April 2012

  • Fröbel, Julia; Rose, Patrick; Müller, Matthias
  • Philosophical Transactions of the Royal Society B: Biological Sciences, Vol. 367, Issue 1592
  • DOI: 10.1098/rstb.2011.0202

Twin-arginine-dependent translocation of folded proteins
journal, April 2012

  • Fröbel, Julia; Rose, Patrick; Müller, Matthias
  • Philosophical Transactions of the Royal Society B: Biological Sciences, Vol. 367, Issue 1592
  • DOI: 10.1098/rstb.2011.0202

Transport of Folded Proteins by the Tat System
journal, August 2019


Routing of thylakoid lumen proteins by the chloroplast twin arginine transport pathway
journal, August 2018

  • New, Christopher Paul; Ma, Qianqian; Dabney-Smith, Carole
  • Photosynthesis Research, Vol. 138, Issue 3
  • DOI: 10.1007/s11120-018-0567-z

The twin-arginine transport system: moving folded proteins across membranes
journal, October 2007


The Chloroplast Tat Pathway Transports Substrates in the Dark
journal, January 2008

  • Braun, Nikolai A.; Theg, Steven M.
  • Journal of Biological Chemistry, Vol. 283, Issue 14
  • DOI: 10.1074/jbc.m708948200

The Tat protein transport system: intriguing questions and conundrums
journal, May 2018

  • Hamsanathan, Shruthi; Musser, Siegfried M.
  • FEMS Microbiology Letters, Vol. 365, Issue 12
  • DOI: 10.1093/femsle/fny123

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