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Two forms of the ph...
Two forms of the photosystem II D1 protein alter energy dissipation and state transitions in the cyanobacterium Synechococcus sp PCC 7942
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Campbell, D (författare)
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Bruce, D (författare)
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Carpenter, C (författare)
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visa fler...
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- Gustafsson, Petter, 1948- (författare)
- Umeå universitet,Institutionen för fysiologisk botanik,Umeå Plant Science Centre (UPSC)
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- Oquist, Gunnar, 1941- (författare)
- Umeå universitet,Institutionen för fysiologisk botanik,Umeå Plant Science Centre (UPSC)
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visa färre...
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(creator_code:org_t)
- 1996
- 1996
- Engelska.
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Ingår i: Photosynthesis Research. - 0166-8595 .- 1573-5079. ; 47:2, s. 131-144
- Relaterad länk:
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https://urn.kb.se/re...
Abstract
Ämnesord
Stäng
- Synechococcus sp. PCC 7942 (Anacystis nidulans R2) contains two forms of the Photosystem II reaction centre protein D1, which differ in 25 of 360 amino acids. D1:1 predominates under low light hut is transiently replaced by D1:2 upon shifts to higher light. Mutant cells containing only D1:1 have lower photochemical energy capture efficiency and decreased resistance to photoinhibition, compared to cells containing D1:2. We show that when dark-adapted or under low to moderate light, cells with D1:1 have higher non-photochemical quenching of PS II fluorescence (higher q(N)) than do cells with D1:2. This is reflected in the 77 K chlorophyll emission spectra, with lower Photosystem II fluorescence at 697-698 nm in cells containing D1:1 than in cells with D1:2. This difference in quenching of Photosystem II fluorescence occurs upon excitation of both chlorophyll at 435 nm and phycobilisomes at 570 nm. Measurement of time-resolved room temperature fluorescence shows that Photosystem II fluorescence related to charge stabilization is quenched more rapidly in cells containing D1:1 than in those with D1:2. Cells containing D1:1 appear generally shifted towards State II, with PS II down-regulated, while cells with D1:2 tend towards State I. In these cyanobacteria electron transport away from PS II remains non-saturated even under photoinhibitory levels of light. Therefore, the higher activity of D1:2 Photosystem II centres may allow more rapid photochemical dissipation of excess energy into the electron transport chain. D1:1 confers capacity for extreme State II which may be of benefit under low and variable light.
Nyckelord
- chlorophyll fluorescence
- electron transport
- light-acclimation
- light-harvesting
- photosynthesis
- quenching analysis
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