The Molecular Concept of Protein Translocation across the Outer Membrane of Chloroplasts

Vojta, Aleksandar; Fulgosi, Hrvoje; Schleiff, Enrico (2008) The Molecular Concept of Protein Translocation across the Outer Membrane of Chloroplasts. Croatica Chemica Acta, 81 (3). pp. 501-509. ISSN 0011-1643

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Abstract

Chloroplasts, plant organelles which facilitate photosynthesis, originated when photosynthetic bacteria became a part of non-photosynthetic eukaryotic cell. Chloroplast proteins synthetised in the cytosol have to be transported into the organelle, which is facilitated by the Toe complex on the Outer envelope. The preprotein receptors Toc34 and Toc159 associate with the pore-forming Toc75 to form the Toe core complex. Toc64 and Toc 12 dynamically associate with the core complex and recruit chaperones, forming the intermembrane space complex. Describing Toc159 as integral membrane protein provides insight into its function. After receiving preproteins from Toc34, it uses GTP hydrolysis to push the precursor into the translocation channel. GTP hydrolysis by Toc34 controls its binding/handover cycle. Moreover, different isoforms of Toe components form complexes with different specificity for photosynthetic and non-photosynthetic preproteins. After initial translocation steps, a series of binding spots seems to constitute an affinity chain that guides preproteins further on their translocation pathway. This model parallels the "acid chain" described in mitochondrial import. Considering recent data, a new "big picture" of chloroplast import begins to emerge.

Item Type:	Article
Uncontrolled Keywords:	chloroplasts; envelope membranes; GTPase; protein receptors; translocation channel; phosphorylation; import receptor; envelope membranes; precursor proteins; transit peptide; preprotein translocon; endosymbiotic origin; acid chain; toc34; phosphorylation; components
Subjects:	NATURAL SCIENCES > Chemistry
Divisions:	Division of Molecular Biology
Projects:	Project title Project leader Project code Project type Normizacija nekih pokazatelja zdravlja hrvatskih izvornih pasmina ovaca [104775] Miljenko Šimpraga 053-1780469-2110 MZOS Utjecaj oksidativnog stresa na organizaciju i funkciju biljnih stanica i tkiva [221446] Hrvoje Lepeduš 073-0731674-1673 MZOS Regulatorni mehanizmi fotosinteze i diferencijacija plastida [186771] Hrvoje Fulgosi 098-0982913-2838 MZOS
Depositing User:	Hrvoje Fulgosi
Date Deposited:	23 Oct 2013 08:54
URI:	http://fulir.irb.hr/id/eprint/830

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