Structure of the plant photosystem I

Ido Caspy, Nathan Nelson*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review


Plant photosystem I (PSI) is one of the most intricate membrane complexes in nature. It comprises two complexes, a reaction center and light-harvesting complex (LHC), which together form the PSI–LHC supercomplex. The crystal structure of plant PSI was solved with two distinct crystal forms. The first, crystallized at pH 6.5, exhibited P21 symmetry; the second, crystallized at pH 8.5, exhibited P212121 symmetry. The surfaces involved in binding plastocyanin and ferredoxin are identical in both forms. The crystal structure at 2.6 Å resolution revealed 16 subunits, 45 transmembrane helices, and 232 prosthetic groups, including 143 chlorophyll a, 13 chlorophyll b, 27 β-carotene, 7 lutein, 2 xanthophyll, 1 zeaxanthin, 20 monogalactosyl diglyceride, 7 phosphatidyl diglyceride, 5 digalactosyl diglyceride, 2 calcium ions, 2 phylloquinone, and 3 iron sulfur clusters. The model reveals detailed interactions, providing mechanisms for excitation energy transfer and its modulation in one of nature’s most efficient photochemical machine.

Original languageEnglish
Pages (from-to)285-294
Number of pages10
JournalBiochemical Society Transactions
Issue number2
StatePublished - 17 Apr 2018


FundersFunder number
Secretaría de Educación Pública
H2020 European Research Council
European Research Council
European Synchrotron Radiation Facility
Israel Science Foundation569/17
Planning and Budgeting Committee of the Council for Higher Education of Israel1775/12


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