TIC/TOC complex

<h2 id="tomtim-complex-vs-toctic-complex">TOM/TIM complex vs. TOC/TIC complex</h2>

<p>This protein complex is functionally similar to the <a href="/facts/TIM/TOM_complex/9xnCAJcF">TOM/TIM Complex</a> located on the outer and inner membranes of the mitochondria, in the sense that it too transports proteins across multiple membranes and into the lumen of an organelle. Both complexes (TOC/TIC) are GTPases, that is, they must both hydrolyze GTP in order to power the translocation. The chloroplast also harnesses the power of an electrochemical gradient using protons. The gradient is only used to power transport across the thylakoid membrane, however, while the gradient in the mitochondria is used to power transport across its inner membrane.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
</p><p>Furthermore, due to the thylakoid membrane located inside of the chloroplast, a second transit peptide sequence must be located on the imported protein. In the cytosol, a transit peptide that signals for transit of the protein to the chloroplast is exposed. This initiates transport and translocation through the TIC/TOC complexes into the stroma of the chloroplast. It is there that a signal peptidase cleaves the stromal transit peptide, only to reveal a second transit peptide sequence underneath; this time directing to the thylakoid membrane.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> There are at least three ways for the protein to go through the thylakoid membrane: through a ATP-hydrolyzing <a href="/facts/Type_II_secretion_system/vyf2rqyf">Type II secretion system</a>, through a <a href="/facts/SecY_protein/8XVhUN3u">SecY</a> translocon, or through the <a href="/facts/Twin-arginine_translocation_pathway/gNmm2TPS">Tat/VSP pathway</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
</p>

<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Chloroplast_DNA/UGscJVan">Chloroplast DNA</a></li>
<li><a href="/facts/Chloroplast/fo8U3yTx">Chloroplast</a></li></ul>

<h2 id="external-links">External links</h2>
<ul><li><a href="/facts/TCDB/ffVr4nQQ">TCDB</a> <a href="http://www.tcdb.org/search/result.php?tc=3.A.9">3.A.9</a> - description of the entire complex</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Stengel A, Benz JP, Buchanan BB, Soll J, Bölter B (November 2009). "Preprotein import into chloroplasts via the Toc and Tic complexes is regulated by redox signals in Pisum sativum". Molecular Plant. 2 (6): 1181–97. doi:10.1093/mp/ssp043. PMID 19995724. <a href="https://doi.org/10.1093%2Fmp%2Fssp043" target="_blank">https://doi.org/10.1093%2Fmp%2Fssp043</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P. Molecular biology of the cell (4th ed.). Garland Science. ISBN 978-0-8153-3218-3. <a href="978-0-8153-3218-3" target="_blank">978-0-8153-3218-3</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Li HM, Chiu CC (2010). "Protein transport into chloroplasts". Annual Review of Plant Biology. 61: 157–80. doi:10.1146/annurev-arplant-042809-112222. PMID 20192748. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Rolland, V; Rae, BD; Long, BM (2 November 2017). "Setting sub-organellar sights: accurate targeting of multi-transmembrane-domain proteins to specific chloroplast membranes". Journal of Experimental Botany. 68 (18): 5013–5016. doi:10.1093/jxb/erx351. PMC 5853405. PMID 29106623. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5853405" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5853405</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
</ol>

TIC/TOC complex open-in-new

TIC/TOC complex