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.
|Number of pages||10|
|Journal||Biochimica et Biophysica Acta|
|Publication status||Published - 1990|
- Electron microscopy
- Reaction center complex
- Chlorophyll a1
- Photosystem I