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| Subject Categories: Membranes & Transport | Proteins |
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| The EMBO Journal
(2007) 26, 3039–3049, doi:10.1038/sj.emboj.7601759 Published online 14 June 2007 |
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| Evidence for a dynamic and transient pathway through the TAT protein transport machinery |
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| Kenneth Cline and Michael McCaffery |
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Horticultural Sciences Department and Plant Molecular and Cellular Biology, University of Florida, Gainesville FL, USA To whom correspondence should be addressed Kenneth Cline, Horticultural Sciences, University of Florida, 1109 Fifield Hall, Box 110690, Gainesville, FL 32611, USA. Tel.: +1 352 392 4711 ext. 219; Fax: +1 352 392 5653; E-mail: kcline@ufl.edu Received 12 March 2007; Accepted 22 May 2007; Published online 14 June 2007. |
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| Abstract |
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| Tat systems transport completely folded proteins across ion-tight membranes. Three membrane proteins comprise the Tat machinery in most systems. In thylakoids, cpTatC and Hcf106 mediate precursor recognition, whereas Tha4 facilitates translocation. We used chimeric precursor proteins with unstructured peptides and folded domains to test predictions of competing translocation models. Two models invoke protein-conducting channels, whereas another model proposes that cpTatC pulls substrates through a patch of Tha4 on the lipid bilayer. The thylakoid system transported unstructured peptide substrates alone or when fused to folded domains. However, larger substrates stalled before completion, some with amino- and carboxyl-folded domains on opposite sides of the membrane. The length of the precursor that resulted in translocation arrest (20 to 30 nm) exceeded that expected for a single 'pull' mechanism, suggesting that a sustained driving force rather than a single pull moves the protein across the bilayer. Three different methods showed that stalled substrates were not stuck in a channel or even associated with Tat machinery. This finding favors the Tha4 patch model for translocation. |
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| Keywords: chloroplasts, protein transport, thylakoid, translocation channel, unstructured peptides |
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Top of page MORE ARTICLES LIKE THISThese links to content published by NPG are automatically generated RESEARCHEvidence for a dynamic and transient pathway through the TAT protein transport machinery The EMBO Journal Article Thylakoid targeting of Tat passenger proteins shows no ΔpH dependence in vivo The EMBO Journal Article (17 Feb 2003) The EMBO Journal Article (06 Aug 2008) The EMBO Journal Article |
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