Mono-, di- and trimeric PS I reaction center complexes isolated from the thermophilic cyanobacterium Synechococcus sp. Size, shape and activity

M. Rögner*, U. Mühlenhoff, E.J. Boekema, H.T. Witt

*Corresponding author for this work

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    Abstract

    Photosystem I preparations from the cyanobacterium Synechococcus sp. were treated with high concentrations of Tris and octyl glucoside at alkaline pH and elevated temperature. A sucrose density gradient yielded three pigment-protein complexes; these were further purified on a HPLC anion-exchange column. In contrast to SDS-PAGE under non-denaturing conditions, this method produces homogeneous, highly active PS I particles in large quantities using mild solubilization conditions. Gel-filtration HPLC, SDS-PAGE, antenna Chl/Chl a1 ratio and electron microscopy images suggest that the three complexes represent monomeric, dimeric and trimeric forms of a minimal reaction center I unit. The size of this monomeric complex is 15.3 × 10.6 × 6.4 nm (length × width × height) as determined by electron microscopy. The apparent molecular mass - including 65 antenna chlorophylls per Chl a1, but excluding the detergent shell - is estimated by three different methods to be (235 ± 25) kDa.
    Original languageEnglish
    Pages (from-to)415-424
    Number of pages10
    JournalBiochimica et Biophysica Acta
    Volume1015
    Publication statusPublished - 1990

    Keywords

    • (Synechococcus)
    • Electron microscopy
    • Reaction center complex
    • HPLC
    • Chlorophyll a1
    • Photosystem I

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