Structure of the plant photosystem I. (27th February 2018)

• Record Type: Journal Article
• Authors: Caspy, Ido; Nelson, Nathan
• Is Part Of: Biochemical Society transactions. Volume 46:Number 2(2018)
• Page Start: 285
• Page End: 294
• Publication Date: 2018-02-27
• Subjects: evolution -- light-harvesting complexes -- membrane complexes -- photosynthesis -- photosystems -- structure; Biochemistry -- Congresses; 572
• DOI: 10.1042/BST20170299
• Languages: English
• ISSNs: 0300-5127

Abstract

Abstract : 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 P 21 symmetry; the second, crystallized at pH 8.5, exhibited P 212121 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.