3D model of an IronStress-induced isiA-PSI supercomplex
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Three-dimensional Model and Characterization of the Iron Stress-induced CP43'-Photosystem I Supercomplex Isolated from the Cyanobacterium Synechocystis PCC 6803 |
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| - adapted from: Thomas S. Bibby, Jon Nield & James Barber. The Journal of Biological Chemistry: 276:43246-43252 | |
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| ABSTRACT: The cyanobacterium Synechocystis PCC 6803 has been subjected to growth under iron-deficient conditions. As a consequence, the isiA gene is expressed, and its product, the chlorophyll a-binding protein CP43', accumulates in the cell. Recently, we have shown for the first time that 18 copies of this photosystem II (PSII)-like chlorophyll a-binding protein forms a ring around the trimeric photosystem I (PSI) reaction center (Bibby, T. S., Nield, J., and Barber, J. (2001) Nature, 412, 743- 745). Here we further characterize the biochemical and structural properties of this novel CP43'-PSI supercomplex confirming that it is a functional unit of approximately 1900 kDa where the antenna size of PSI is increased by 70% or more. Using electron microscopy and single particle analysis, we have constructed a preliminary three-dimensional model of the CP43'-PSI supercomplex and used it as a framework to incorporate higher resolution structures of PSI and CP43 recently derived from x-ray crystallography. Not only does this work emphasize the flexibility of cyanobacterial lightharvesting systems in response to the lowering of phycobilisome and PSI levels under iron-deficient conditions, but it also has implications for understanding the organization of the related chlorophyll a/b-binding Pcb proteins of oxychlorobacteria, formerly known as prochlorophytes.. CONTENTS Also, click on the figures! | |
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| Straight to Introduction | |
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© Journal of Biological Chemistry, 2001