| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2000: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1999: ¥3,000,000 (Direct Cost: ¥3,000,000)
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| Research Abstract |
The two dimensional crystals of spinach PSII subcore complexes consisting of CP47, D1, D2, cytochrome b-559 and psbI gene product were prepared and the crystals were examined by electron microscopy and atomic force microscopy. Comparison of the surface topography with the electron microscopic projection map of the 2D crystal, by taking into account the asymmetric mass distribution predicted from the membrane-protruding parts of the complex, revealed that the observed ridges corresponded only to the lumenal-protruding domains of the PSH complex, while the rather flat stromal-protruding domains were neglected. Cross section analysis of the 2D crystals indicated that the whole thickness of the PSII subcore complex was 6.4±0.2 nm, and the lumenal domain was higher than the stromal domain by 1.0±0.2 nm. By assuming the thickness of the lipid bilayer to be 3.5 nm according to the estimation from our three dimensional electron microscopy of negatively stained 2D crystals, the height of the lumenal and stromal domains above the lipid bilayer surface were estimated to be 2.0 nm and 1.0 nm, respectively. Three-dimensional structure of PSII oxygen-evolving complex (PSIIOEC), composed of CP47, CP43, D1, D2, cytochromeb-559 andpsbI gene product and 33-kDa extrinsic protein, was revealed at 22Å resolution by single particle analysis from electron micrographs of PSIIOEC dimers negatively stained with uranyl acetate. The thickness of the edge region is 40Å, suggesting that the most of this domain is embedded in lipid bilayer Two protrusions for each monomer elongate from tne lumenal side. One protrusion locates between CP47 and D2 protein and can be assigned as 33-kDa extrinsic protain and a large loop E of CP47. However, another protrusion exists on the lumenal side between D1 and CP43 even in the absence of 23-kDa / 17-kDa proteins. It is preferable to assign this protrusion to the long lumenal loop (loop E) of CP43 extending to D1.
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