9LZK

The PSI1-IsiA13 complex with double-layered IsiA proteins bound to the monomeric PSI core

Summary for 9LZK

• Entry DOI: 10.2210/pdb9lzk/pdb
• EMDB information: 63528
• Descriptor: Iron stress-induced chlorophyll-binding protein, Photosystem I reaction center subunit PsaK, Photosystem I reaction center subunit XII, ... (20 entities in total)
• Functional Keywords: photosystem-antenna complex, photosynthesis
• Biological source: Thermosynechococcus vestitus BP-1; More
• Total number of polymer chains: 24
• Total formula weight: 1095126.84

Authors

Si, L.,Cao, P.,Li, M. (deposition date: 2025-02-21, release date: 2025-12-31, Last modification date: 2026-01-28)

Primary citation

Si, L.,Zhang, Y.,Su, X.,Zhao, X.,An, X.,Liu, L.N.,Cao, P.,Li, M.
Structural basis for the assembly and energy transfer between the cyanobacterial PSI core and the double-layered IsiA proteins.
Nat Commun, 17:592-592, 2025

PubMed Abstract: Iron-limitation is a common stress factor in natural environments. To survive under iron-starved conditions, cyanobacteria overexpress iron stress-induced protein A (IsiA), which is crucial for light-harvesting and photoprotection. Multiple IsiA proteins form a single- or double-layered architecture encircling the photosystem I (PSI) core, forming various PSI-IsiA supercomplexes. The assembly and energy transfer mechanisms of double-layered PSI-IsiA supercomplexes remain unelucidated. Here, we present high-resolution structures of two PSI-IsiA supercomplexes isolated from the cyanobacterium Thermosynechococcus elongatus BP-1 cultured under iron-starved conditions. The PSI-IsiA complex contains a trimeric PSI core surrounded by 43 IsiA subunits assembled into a closed double-ring. The PSI-IsiA complex contains 13 IsiA proteins arranged in a double-layered architecture attached to the monomeric PSI core. Atomic force microscopy demonstrates the presence and distribution of different PSI-IsiA complexes within native thylakoid membranes isolated from iron-starved cells. Our findings provide insights into the structural variability and adaptive mechanisms of PSI-IsiA complexes.

PubMed: 41422266
DOI: 10.1038/s41467-025-67295-2

Experimental method

ELECTRON MICROSCOPY (3.5 Å)