The structure of the stress-induced photosystem I–IsiA antenna supercomplex

Toporik, Hila; Li, Jin; Williams, Dewight; Chiu, Po-Lin; Mazor, Yuval

doi:10.1038/s41594-019-0228-8

Cited by 62 publications

(136 citation statements)

References 40 publications

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“…These results indicate that IsiA4 might be a key subunit for the assembly of the octadecameric IsiA ring around the PSI core with specific interactions at its C-terminal region. This is apparently different from the S_PSI-IsiA structure 35 , where the C-terminus of IsiA contains a flexible amphipathic helix and adopts slightly different orientations at different IsiA positions. The C-terminus of IsiA1-5 in the S_PSI-IsiA is directed to the neighboring IsiA subunit and interacts with the Nterminus of the adjacent monomer, whereas the C-terminus of IsiA6 appears to be disordered.…”

Section: Resultscontrasting

confidence: 61%

“…The overall structure and pigment organization of T_PSI-IsiA are similar to those of S_PSI-IsiA 35 . However, compared with the S_PSI-IsiA structure, the T_PSI-IsiA structure has an additional PsaX subunit in the PSI core and there are some differences in the positions of several Chls associated with the PsaX subunit or located near the PsaX position between T_PSI-IsiA and S_PSI-IsiA ( Supplementary Fig.…”

Section: Resultsmentioning

confidence: 76%

“…To find EET pathways between IsiAs, we calculated the Förster energy transfer rates 3,12,35,38,39 between IsiAs (Supplementary Table 4). Common EET pathways, which are defined by a half-life time of <20 ps, are found between all neighboring IsiA pairs (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Förster energy transfer rate calculation. Förster energy transfer rates were calculated according to the Förster theory 3,12,35,38,39 . The Förster energy transfer rate K DA is defined as K DA = (C AA κ 2 )/(n 4 R DA 6 ), where C AA is a factor calculated from the overlap integral between Chls, κ 2 is the dipole orientation factor, n is the refractive index and R DA is the distance between magnesium of Chls.…”

Section: Methodsmentioning

confidence: 99%

“…PCC 6803, and PSI-IsiA from S. sp. PCC 6803 is designated as S_PSI-IsiA) by cryoelectron microscopy (cryo-EM) 35 . The structure showed that 18 IsiAs surround a PSI core trimer in a single ring organization, and implicated that IsiA may function in either energy harvesting or quenching 35 .…”

mentioning

confidence: 99%

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Structure of a cyanobacterial photosystem I surrounded by octadecameric IsiA antenna proteins

et al. 2020

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Iron-stress induced protein A (IsiA) is a chlorophyll-binding membrane-spanning protein in photosynthetic prokaryote cyanobacteria, and is associated with photosystem I (PSI) trimer cores, but its structural and functional significance in light harvesting remains unclear. Here we report a 2.7-Å resolution cryo-electron microscopic structure of a supercomplex between PSI core trimer and IsiA from a thermophilic cyanobacterium Thermosynechococcus vulcanus. The structure showed that 18 IsiA subunits form a closed ring surrounding a PSI trimer core. Detailed arrangement of pigments within the supercomplex, as well as molecular interactions between PSI and IsiA and among IsiAs, were resolved. Time-resolved fluorescence spectra of the PSI-IsiA supercomplex showed clear excitation-energy transfer from IsiA to PSI, strongly indicating that IsiA functions as an energy donor, but not an energy quencher, in the supercomplex. These structural and spectroscopic findings provide important insights into the excitation-energy-transfer and subunit assembly mechanisms in the PSI-IsiA supercomplex.

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Section: Resultscontrasting

confidence: 61%

Section: Resultsmentioning

confidence: 76%