AKR2A-mediated import of chloroplast outer membrane proteins is essential for chloroplast biogenesis
- 13 January 2008
- journal article
- letter
- Published by Springer Science and Business Media LLC in Nature
- Vol. 10 (2), 220-227
- https://doi.org/10.1038/ncb1683
Abstract
In plant cells, chloroplasts have essential roles in many biochemical reactions and physiological responses1. Chloroplasts require numerous protein components, but only a fraction of these proteins are encoded by the chloroplast genome. Instead, most are encoded by the nuclear genome and imported into chloroplasts from the cytoplasm post-translationally2,3,4,5. Membrane proteins located in the chloroplast outer envelope membrane (OEM) have a critical function in the import of proteins into the chloroplast. However, the biogenesis of chloroplast OEM proteins remains poorly understood. Here, we report that an Arabidopsis ankyrin repeat protein, AKR2A, plays an essential role in the biogenesis of the chloroplast OEM proteins. AKR2A binds to chloroplast OEM protein targeting signals, as well as to chloroplasts. It also displays chaperone activity towards chloroplast OEM proteins, and facilitates the targeting of OEP7 to chloroplasts in vitro. AKR2A RNAi in plants with an akr2b knockout background showed greatly reduced levels of chloroplast proteins, including OEM proteins, and chloroplast biogenesis was also defective. Thus, AKR2A functions as a cytosolic mediator for sorting and targeting of nascent chloroplast OEM proteins to the chloroplast.Keywords
This publication has 29 references indexed in Scilit:
- Import Pathways of Chloroplast Interior Proteins and the Outer-Membrane Protein OEP14 Converge at Toc75Plant Cell, 2004
- An outer envelope membrane component of the plastid protein import apparatus plays an essential role in ArabidopsisThe Plant Journal, 2004
- AIP is a mitochondrial import mediator that binds to both import receptor Tom20 and preproteinsThe Journal of cell biology, 2003
- The targeting of the atToc159 preprotein receptor to the chloroplast outer membrane is mediated by its GTPase domain and is regulated by GTPThe Journal of cell biology, 2002
- Essential role of the G-domain in targeting of the protein import receptor atToc159 to the chloroplast outer membraneThe Journal of cell biology, 2002
- Identification of a Signal That Distinguishes between the Chloroplast Outer Envelope Membrane and the Endomembrane System in VivoPlant Cell, 2001
- Insertion of OEP14 into the Outer Envelope Membrane Is Mediated by Proteinaceous Components of ChloroplastsPlant Cell, 2000
- A glucocorticoid‐mediated transcriptional induction system in transgenic plantsThe Plant Journal, 1997
- Protein targeting and integration signal for the chloroplastic outer envelope membrane.Plant Cell, 1996
- Targeting of proteins to the outer envelope membrane uses a different pathway than transport into chloroplasts.Plant Cell, 1991