Open AccessSupramolecular organization of photosystem II and its light‐harvesting antenna in partially solubilized photosystem II membranes
Author(s) -
Boekema Egbert J.,
van Roon Henny,
van Breemen Jan F. L.,
Dekker Jan P.
Publication year - 1999
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.1999.00876.x
Subject(s) - photosystem ii , trimer , chemistry , photosystem i , light harvesting complex , crystallography , thylakoid , p700 , biophysics , supramolecular chemistry , membrane , photosynthesis , biology , chloroplast , biochemistry , dimer , organic chemistry , crystal structure , gene
We present an extended analysis of the organization of green plant photosystem II and its associated light‐harvesting antenna using electron microscopy and image analysis. The analysis is based on a large dataset of 16 600 projections of negatively stained PSII–LHCII supercomplexes and megacomplexes prepared by means of three different pretreatments. In addition to our previous work on this system [Boekema, E.J., van Roon, H., Calkoen, F., Bassi, R. and Dekker, J.P. (1999) Biochemistry 38 , 2233–2239], the following results were obtained. The rotational orientation of trimeric LHCII at the S, M and L binding positions was determined. It was found that compared to the S trimer, the M and L trimers are rotationally shifted by about −20° and −50°, respectively. The number of projections with empty CP29, CP26 and CP24 binding sites was found to be about 0, 18 and 4%, respectively. We suggest that CP26 and CP24 are not required for the binding of trimeric LHCII at any of the three binding positions. A new type of megacomplex was observed with a characteristic windmill‐like shape. This type III megacomplex consists of two C 2 S 2 supercomplexes connected at their CP26 tips. Structural variation in the region of the central dimeric photosystem II complex was found to occur at one specific position near the periphery of the complex. We attribute this variation to the partial absence of an extrinsic polypeptide or one or more small intrinsic membrane proteins.