Structural basis of metabolite transport by the chloroplast outer envelope channel OEP21

Umut Günsel, Kai Klöpfer, Elisabeth Häusler, Manuel Hitzenberger, Bettina Bölter, Laura E. Sperl, Martin Zacharias, Jürgen Soll, Franz Hagn

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Triose phosphates (TPs) are the primary products of photosynthetic CO2 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 C3 plants. OEP21 is a cone-shaped β-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.

Original languageEnglish
Pages (from-to)761-769
Number of pages9
JournalNature Structural and Molecular Biology
Issue number6
StatePublished - Jun 2023
Externally publishedYes


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