Structural basis for energy and electron transfer of the photosystem I–IsiA–flavodoxin supercomplex
Under iron-deficiency stress, which occurs frequently in natural aquatic environments, cyanobacteria reduce the amount of iron-enriched proteins, including photosystem I (PSI) and ferredoxin (Fd), and upregulate the expression of iron-stress-induced proteins A and B (IsiA and flavodoxin (Fld)). Mult...
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Veröffentlicht in: | Nature plants 2020-02, Vol.6 (2), p.167-176 |
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Zusammenfassung: | Under iron-deficiency stress, which occurs frequently in natural aquatic environments, cyanobacteria reduce the amount of iron-enriched proteins, including photosystem I (PSI) and ferredoxin (Fd), and upregulate the expression of iron-stress-induced proteins A and B (IsiA and flavodoxin (Fld)). Multiple IsiAs function as the peripheral antennae that encircle the PSI core, whereas Fld replaces Fd as the electron receptor of PSI. Here, we report the structures of the PSI
3
–IsiA
18
–Fld
3
and PSI
3
–IsiA
18
supercomplexes from
Synechococcus sp
. PCC 7942, revealing features that are different from the previously reported PSI structures, and a sophisticated pigment network that involves previously unobserved pigment molecules. Spectroscopic results demonstrated that IsiAs are efficient light harvesters for PSI. Three Flds bind symmetrically to the trimeric PSI core—we reveal the detailed interaction and the electron transport path between PSI and Fld. Our results provide a structural basis for understanding the mechanisms of light harvesting, energy transfer and electron transport of cyanobacterial PSI under stressed conditions.
Cyanobacterial photosystem I supercomplexes bind to iron-stress-induced proteins IsiA and flavodoxin under iron-deficiency conditions. They form a network that is highly efficient at light harvesting and retains normal electron transport efficiency. |
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ISSN: | 2055-026X 2055-0278 2055-0278 |
DOI: | 10.1038/s41477-020-0593-7 |