7bw2

Crystal Structure of Cyanobacterial PSI Monomer from T.elongatus at 6.5 A ResolutionCrystal Structure of Cyanobacterial PSI Monomer from T.elongatus at 6.5 A Resolution

Structural highlights

7bw2 is a 10 chain structure with sequence from Thermosynechococcus vestitus BP-1. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 6.5Å
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

PSAA_THEVB PsaA and PsaB bind P700, the primary electron donor of photosystem I (PSI), as well as the electron acceptors A0, A1 and FX. PSI is a plastocyanin/cytochrome c6-ferredoxin oxidoreductase, converting photonic excitation into a charge separation, which transfers an electron from the donor P700 chlorophyll pair to the spectroscopically characterized acceptors A0, A1, FX, FA and FB in turn. Oxidized P700 is reduced on the lumenal side of the thylakoid membrane by plastocyanin or cytochrome c6.^[1] ^[2] ^[3] ^[4]

Publication Abstract from PubMed

A high-resolution structure of trimeric cyanobacterial Photosystem I (PSI) from Thermosynechococcus elongatus was reported as the first atomic model of PSI almost 20 years ago. However, the monomeric PSI structure has not yet been reported despite long-standing interest in its structure and extensive spectroscopic characterization of the loss of red chlorophylls upon monomerization. Here, we describe the structure of monomeric PSI from Thermosynechococcus elongatus BP-1. Comparison with the trimer structure gave detailed insights into monomerization-induced changes in both the central trimerization domain and the peripheral regions of the complex. Monomerization-induced loss of red chlorophylls is assigned to a cluster of chlorophylls adjacent to PsaX. Based on our findings, we propose a role of PsaX in the stabilization of red chlorophylls and that lipids of the surrounding membrane present a major source of thermal energy for uphill excitation energy transfer from red chlorophylls to P700.

Cryo-EM structure of a functional monomeric Photosystem I from Thermosynechococcus elongatus reveals red chlorophyll cluster.,Coruh O, Frank A, Tanaka H, Kawamoto A, El-Mohsnawy E, Kato T, Namba K, Gerle C, Nowaczyk MM, Kurisu G Commun Biol. 2021 Mar 8;4(1):304. doi: 10.1038/s42003-021-01808-9. PMID:33686186^[5]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Klukas O, Schubert WD, Jordan P, Krauss N, Fromme P, Witt HT, Saenger W. Photosystem I, an improved model of the stromal subunits PsaC, PsaD, and PsaE. J Biol Chem. 1999 Mar 12;274(11):7351-60. PMID:10066799
↑ Klukas O, Schubert WD, Jordan P, Krau N, Fromme P, Witt HT, Saenger W. Localization of two phylloquinones, QK and QK', in an improved electron density map of photosystem I at 4-A resolution. J Biol Chem. 1999 Mar 12;274(11):7361-7. PMID:10066800
↑ Jordan P, Fromme P, Witt HT, Klukas O, Saenger W, Krauss N. Three-dimensional structure of cyanobacterial photosystem I at 2.5 A resolution. Nature. 2001 Jun 21;411(6840):909-17. PMID:11418848 doi:10.1038/35082000
↑ Krauss N, Schubert WD, Klukas O, Fromme P, Witt HT, Saenger W. Photosystem I at 4 A resolution represents the first structural model of a joint photosynthetic reaction centre and core antenna system. Nat Struct Biol. 1996 Nov;3(11):965-73. PMID:8901876
↑ Çoruh O, Frank A, Tanaka H, Kawamoto A, El-Mohsnawy E, Kato T, Namba K, Gerle C, Nowaczyk MM, Kurisu G. Cryo-EM structure of a functional monomeric Photosystem I from Thermosynechococcus elongatus reveals red chlorophyll cluster. Commun Biol. 2021 Mar 8;4(1):304. PMID:33686186 doi:10.1038/s42003-021-01808-9

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OCA

[1] Klukas O, Schubert WD, Jordan P, Krauss N, Fromme P, Witt HT, Saenger W. Photosystem I, an improved model of the stromal subunits PsaC, PsaD, and PsaE. J Biol Chem. 1999 Mar 12;274(11):7351-60. PMID:10066799

[2] Klukas O, Schubert WD, Jordan P, Krau N, Fromme P, Witt HT, Saenger W. Localization of two phylloquinones, QK and QK', in an improved electron density map of photosystem I at 4-A resolution. J Biol Chem. 1999 Mar 12;274(11):7361-7. PMID:10066800

[3] Jordan P, Fromme P, Witt HT, Klukas O, Saenger W, Krauss N. Three-dimensional structure of cyanobacterial photosystem I at 2.5 A resolution. Nature. 2001 Jun 21;411(6840):909-17. PMID:11418848 doi:10.1038/35082000

[4] Krauss N, Schubert WD, Klukas O, Fromme P, Witt HT, Saenger W. Photosystem I at 4 A resolution represents the first structural model of a joint photosynthetic reaction centre and core antenna system. Nat Struct Biol. 1996 Nov;3(11):965-73. PMID:8901876

[5] Çoruh O, Frank A, Tanaka H, Kawamoto A, El-Mohsnawy E, Kato T, Namba K, Gerle C, Nowaczyk MM, Kurisu G. Cryo-EM structure of a functional monomeric Photosystem I from Thermosynechococcus elongatus reveals red chlorophyll cluster. Commun Biol. 2021 Mar 8;4(1):304. PMID:33686186 doi:10.1038/s42003-021-01808-9

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