Molecular arrangement of pigment-protein complex of photosystem 1 |
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Authors: | V V Shubin N V Karapetyan A A Krasnovsky |
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Institution: | (1) A.N. Bakh Institute of Biochemistry, USSR Academy of Sciences, 117071 Moscow, USSR |
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Abstract: | The circular dichroism (CD) method was applied to study the molecular organization of P700, antenna chlorophyll and protein of photosystem 1 complexes (CP1), isolated from chloroplasts under mild treatment with Triton X-100. Analysis of CD spectra and protein: chlorophyll: P700 ratios for CP1 complexes that were different in their chlorophyll content indicate that CP1 preparations can be considered as a mixture of CP1-RC, containing P700 (10–20%), and CP1-LH without P700 (80–90%). Both types of complexes contain approximately 25 chlorophyll molecules, and the destruction of their spatial organization with detergents represents a cooperative transition. The rate of chlorophyll destruction in CP1-LH is much higher than that in CP1-RC. In both complexes a 65 kDa polypeptide predominates, whose secondary structure (typical for / proteins) is stable to Triton X-100 and does not depends on the chlorophyll content. Chlorophyll seems to be grouped in clusters (5–7 molecules) in the hydrophobic cores of 2–3 parallel / domains of the 65 kDa protein. Only one of the clusters in CP1-RC includes P700; on P700 photooxidation the change of its interaction with the nearest pigment environment results in a complicated shape of the light-induced CD spectra.Abbreviations PS1
photosystem 1
- CP1
pigment-protein complex of PS1
- Chl
chlorophyll a
- CP1-140
CP1 with ratio Ch1:P700 140
- RC
reaction center
- LH
light-harvesting pigment
- CP1-RC
CP1, containing P700
- CP1-LH
CP1 without P700 (containing LH)
- CD
circular dichroism
- SDS
sodium dodecyl sulfate
Dedicated to Prof. L.N.M. Duysens on the occasion of his retirement |
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Keywords: | light-harvesting complex (pea) cPII optical absorption linear dichroism chroism protein secondary structure |
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