The plastoquinone diffusion coefficient in chloroplasts and its mechanistic implications

Blackwell, Mary F.; Gibas, Cynthia; Gygax, Scott E.; Roman, Debra; Wagner, Brandee

doi:10.1016/0005-2728(94)90081-7

Cited by 57 publications

(33 citation statements)

References 42 publications

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“…It should be noted, however, that these proposals have generated considerable doubts and controversy. To illustrate, Joliot et al (1992) concluded that plastoquinone cannot be responsible for the long range diffusion involved in rapid electron transfer from granal (PS II) to stromal (PSI) regions, a role that must be fulfilled by plastocyanin -a conclusion also reached by Blackwell et al (1994). The unsuitability of plastoquinone as an electron shuttle between photosystems was likewise the conclusion reached by Albertsson and associates (Yu et al 1993) in their work with a highly purified PS II preparation.…”

Section: Reassessments and Quantum Requirementsmentioning

confidence: 62%

Divergent pathways of photosynthetic electron transfer: The autonomous oxygenic and anoxygenic photosystems

Arnon

1995

Photosynth Res

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The aim of this article is to assemble and integrate, from a personal perspective of a research participant, seldom examined evidence that is incompatible with some basic tenets of photosynthetic electron transport, the cornerstone of which is the Z scheme. The nonconforming evidence pertaining to the mode of ferredoxin reduction and the role of the copper redox protein, plastocyanin, indicates that contrary to the Z scheme ferredoxin is reduced in two experimentally distinguishable ways: oxygenically by PS II (renamed the oxygenic photosystem), without the participation of PS I, and anoxygenically by PS I (renamed the anoxygenic photosystem). It also indicates that plastocyanin is not only, as the Z scheme asserts, the electron donor to the reaction center chlorophyll of PS I (P700) but also to the reaction center chlorophyll of PS II (P680). Other unconventional findings include evidence that the fully functional oxygenic photosystem, when operating separately from the anoxygenic photosystem, reduces plastoquinone to plastoquinol and subsequently oxidizes plastoquinol by two pathways acting in concert: one being the universally recognized DBMIB-sensitive pathway via the Rieske iron-sulfur center of the cytochrome bf complex and the other, a hitherto unrecognized, DBMIB-insensitive electron transport pathway around P680 that centers on cytochrome b-559. These nonconforming findings form the basis of an alternate hypothesis of photosynthetic electron transport that modifies and complements the Z scheme.

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Section: Reassessments and Quantum Requirementsmentioning

confidence: 62%

Divergent pathways of photosynthetic electron transfer: The autonomous oxygenic and anoxygenic photosystems

Arnon

1995

Photosynth Res

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“…Unlike artificial liposomes, thylakoid membranes are crowded with macromolecular complexes (Kirchhoff et al, 2002;Olive et al, 1997;Westermanni et al, 1999). Consequently, PQ motion is severely obstructed by integral proteins in thylakoids (Blackwell et al, 1994;Kirchhoff et al, 2002) compared with that in liposomes (Blackwell et al, 1987). The presence of Ccr2 may be required to keep the PQ in motion in the crowded environment of thylakoids.…”

Section: Discussionmentioning

confidence: 99%

Identification of a novel thylakoid protein gene involved in cold acclimation in cyanobacteria

Gao

Yin

et al. 2012

Microbiology

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In cyanobacteria, genes involved in cold acclimation can be upregulated in response to cold stress with or without light. By inactivating 17 such genes in Synechocystis sp. PCC 6803, slr0815 (ccr2) was identified to be a novel gene required for survival at 15 6C. It was upregulated by cold stress in the light. Upon exposure to low temperature, a ccr2-null mutant showed greatly reduced photosynthetic and respiratory activities within 12 h relative to the wild-type. At 48 h, the photosystem (PS)II-mediated electron transport in the mutant was reduced to less than one-third of the wild-type level, and the duration of electron transfer from the Q B binding site of PSII to PSI was increased to about eight times the wild-type level, whereas the PSI-mediated electron transport remained unchanged. Using an antibody against GFP, a Ccr2-GFP fusion protein was localized to the thylakoid membrane rather than the cytoplasmic and outer membranes. Homologues to Ccr2 can be found in most cyanobacteria, algae and higher plants with sequenced genomes. Ccr2 is probably representative of a group of novel thylakoid proteins involved in acclimation to cold or other stresses.

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“…(2) Blackwell et al (1994) showed that the diffusion coefficient of plastoquinone in thylakoids, (0.1-3) 10 -9 cm 2 s-l, is about two orders of magnitude smaller than the diffusion coefficient in liposomes, probably as a result of macromolecular crowding of the thylakoid membrane proteins.…”

Section: Lack Of a Candidate For A Long Range Mobile Carriermentioning

confidence: 99%

The structure and function of the chloroplast photosynthetic membrane ? a model for the domain organization

Albertsson¹

1995

Photosynth Res

123

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Recent work on the domain organization of the thylakoid is reviewed and a model for the thylakoid of higher plants is presented. According to this model the thylakoid membrane is divided into three main domains: the stroma lamellae, the grana margins and the grana core (partitions). These have different biochemical compositions and have specialized functions. Linear electron transport occurs in the grana while cyclic electron transport is restricted to the stroma lamellae. This model is based on the following results and considerations. (1) There is no good candidate for a long-range mobile redox carrier between PS II in the grana and PS I in the stroma lamellae. The lateral diffusion of plastoquinone and plastocyanin is severely restricted by macromolecular crowding in the membrane and the lumen respectively. (2) There is an excess of 14±18% chlorophyll associated with PS I over that of PS II. This excess is assumed to be localized in the stroma lamellae where PS I drives cyclic electron transport. (3) For several plant species, the stroma lamellae account for 20±3% of the thylakoid membrane and the grana (including the appressed regions, margins and end membranes) for the remaining 80%. The amount of stroma lamellae (20%) corresponds to the excess (14-18%) of chlorophyll associated with PS I. (4) The model predicts a quantum requirement of about 10 quanta per oxygen molecule evolved, which is in good agreement with experimentally observed values. (5) There are at least two pools of each of the following components: PS I, PS II, cytochrome bf complex, plastocyanin, ATP synthase and plastoquinone. One pool is in the grana and the other in the stroma compartments. So far, it has been demonstrated that the PS I, PS II and cytochrome bf complexes each differ in their respective pools.

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The plastoquinone diffusion coefficient in chloroplasts and its mechanistic implications

Cited by 57 publications

References 42 publications

Divergent pathways of photosynthetic electron transfer: The autonomous oxygenic and anoxygenic photosystems

Divergent pathways of photosynthetic electron transfer: The autonomous oxygenic and anoxygenic photosystems

Identification of a novel thylakoid protein gene involved in cold acclimation in cyanobacteria

The structure and function of the chloroplast photosynthetic membrane ? a model for the domain organization

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