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Structural Analysis of the Reaction Center Light-harvesting Complex I Photosynthetic Core Complex of Rhodospirillum rubrum Using Atomic Force Microscopy

Fotiadis, D. and Qian, P. and Philippsen, A. and Bullough, P. A. and Engel, A. and Hunter, C. N.. (2004) Structural Analysis of the Reaction Center Light-harvesting Complex I Photosynthetic Core Complex of Rhodospirillum rubrum Using Atomic Force Microscopy. Journal of biological chemistry, Vol. 279 , no. 3. pp. 2063-2068.

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Official URL: http://edoc.unibas.ch/dok/A5262407

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Abstract

The bacterium Rhodospirillum rubrum contains a simple photosynthetic system, in which the reaction center (RC) receives energy from the light-harvesting (LH1) complex. We have used high-resolution atomic force microscopy (AFM) to image two-dimensional crystals of the RC-LH1 complex of R. rubrum. The AFM topographs show that the RC-LH1 complex is approximately 94 A in height, the RC-H subunit protrudes from the cytoplasmic face of the membrane by 40 A, and it sits 21 A above the highest point of the surrounding LH1 ring. In contrast, the RC on the periplasmic side is at a lower level than LH1, which protrudes from the membrane by 12 A. The RC-LH1 complex can adopt an irregular shape in regions of uneven packing forces in the crystal; this reflects a likely flexibility in the natural membrane, which might be functionally important by allowing the export of quinol formed as a result of RC photochemistry. Nanodissection of the RC by the AFM tip removes the RC-H subunit and reveals the underlying RC-L and -M subunits. LH1 complexes completely lacking the RC were also found, providing ideal conditions for imaging both rings of LH1 polypeptides for the first time by AFM. In addition, we demonstrate the ellipticity of the LH1 ring at the cytoplasmic and periplasmic sides of the membrane, in both the presence and absence of the RC. These AFM measurements have been reconciled with previous electron microscopy and NMR data to produce a model of the RC-LH1 complex.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Structural Biology (Engel)
UniBasel Contributors:Engel, Andreas H
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:American Society of Biological Chemists
ISSN:0021-9258
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:21
Deposited On:22 Mar 2012 13:23

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