7bgh
From Proteopedia
Solution structure of the chloroplast outer envelope channel OEP21
Structural highlights
FunctionOEP21_PEA Voltage-dependent rectifying anion channel that facilitates the translocation between chloroplast and cytoplasm of phosphorylated carbohydrates such as triosephosphate, 3-phosphoglycerate and inorganic phosphate (Pi) depending of ATP to triosephosphate ratio in the plastidial intermembrane space; in high triosephosphate/ATP conditions (e.g. photosynthesis), export of triosphosphate from chloroplast (outward rectifying channels), but in high ATP/triosephosphate conditions (e.g. dark phase), import of phosphosolutes (inward rectifying channels).[1] [2] Publication Abstract from PubMedTriose phosphates (TPs) are the primary products of photosynthetic CO(2) fixation in chloroplasts, which need to be exported into the cytosol across the chloroplast inner envelope (IE) and outer envelope (OE) membranes to sustain plant growth. While transport across the IE is well understood, the mode of action of the transporters in the OE remains unclear. Here we present the high-resolution nuclear magnetic resonance (NMR) structure of the outer envelope protein 21 (OEP21) from garden pea, the main exit pore for TPs in C(3) plants. OEP21 is a cone-shaped beta-barrel pore with a highly positively charged interior that enables binding and translocation of negatively charged metabolites in a competitive manner, up to a size of ~1 kDa. ATP stabilizes the channel and keeps it in an open state. Despite the broad substrate selectivity of OEP21, these results suggest that control of metabolite transport across the OE might be possible. Structural basis of metabolite transport by the chloroplast outer envelope channel OEP21.,Gunsel U, Klopfer K, Hausler E, Hitzenberger M, Bolter B, Sperl LE, Zacharias M, Soll J, Hagn F Nat Struct Mol Biol. 2023 May 8. doi: 10.1038/s41594-023-00984-y. PMID:37156968[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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