title: Two types of fucoxanthin-chlorophyll-binding proteins I tightly bound to the photosystem I core complex in marine centric diatoms.
abstract: Intact fucoxanthin (Fucox)-chlorophyll (Chl)-binding protein I-photosystem I supercomplexes (FCPI-PSIs) were prepared by a newly developed simple fast procedure from centric diatoms Chaetoceros gracilis and Thalassiosira pseudonana to study the mechanism of their efficient solar energy accumulation. FCPI-PSI purified from C. gracilis contained 252 Chl a, 23 Chl c, 56 Fucox, 34 diadinoxanthin+diatoxanthin, 1 violaxanthin, 21 ß-carotene, and 2 menaquinone-4 per P700. The complex showed a high electron transfer activity at 185,000μmolmg Chl a(-1)·h(-1) to reduce methyl viologen from added cytochrome c6. We identified 14 and 21 FCP proteins in FCPI-PSI of C. gracilis and T. pseudonana, respectively, determined by N-terminal and internal amino acid sequences and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses. PsaO and a red lineage Chla/b-binding-like protein (RedCAP), Thaps3:270215, were also identified. Severe detergent treatment of FCPI-PSI released FCPI-1 first, leaving the FCPI-2-PSI-core complex. FCPI-1 contained more Chl c and showed Chl a fluorescence at a shorter wavelength than FCPI-2, suggesting an excitation-energy transfer from FCPI-1 to FCPI-2 and then to the PSI core. Fluorescence emission spectra at 17K in FCPI-2 varied depending on the excitation wavelength, suggesting two independent energy transfer routes. We formulated a model of FCPI-PSI based on the biochemical assay results.
authors: Graduate School of Life Science, University of Hyogo, Harima Science Garden City, Hyogo 678-1297, Japan. yohei_ikeda@spring8.or.jp
authors: Yohei
authors: Y
authors: Ikeda
authors: Atsushi
authors: A
authors: Yamagishi
authors: Masayuki
authors: M
authors: Komura
authors: Takehiro
authors: T
authors: Suzuki
authors: Naoshi
authors: N
authors: Dohmae
authors: Yutaka
authors: Y
authors: Shibata
authors: Shigeru
authors: S
authors: Itoh
authors: Hiroyuki
authors: H
authors: Koike
authors: Kazuhiko
authors: K
authors: Satoh
mesh_terms: D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism*; D000077194:Chlorophyll A; D061146:Chlorophyll Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D002853:Chromatography, Liquid; D045365:Cytochromes c6 / Q000737:chemistry / Q000378:metabolism*; D017377:Diatoms / Q000166:cytology / Q000378:metabolism*; D005453:Fluorescence; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D010777:Photochemistry; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000378:metabolism*; D053719:Tandem Mass Spectrometry
chemical_list: D061146:Chlorophyll Binding Proteins; D045365:Cytochromes c6; D010446:Peptide Fragments; D045331:Photosystem I Protein Complex; D002734:Chlorophyll; D000077194:Chlorophyll A