Faculty Opinions recommendation of PGR5 is required for efficient Q cycle in the cytochrome b6f complex during cyclic electron flow.

2020 ◽  
Author(s):  
Robert Furbank
Keyword(s):  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Cytochrome B6f Complex ◽  
Cytochrome B6f ◽  
Q Cycle ◽  
B6f Complex

scholarly journals PGR5 is required for efficient Q cycle in the cytochrome b6f complex during cyclic electron flow

2020 ◽  
Vol 477 (9) ◽  
pp. 1631-1650 ◽  
Author(s):  
Felix Buchert ◽  
Laura Mosebach ◽  
Philipp Gäbelein ◽  
Michael Hippler
Keyword(s):  
Electron Transfer ◽  
Reductase Activity ◽  
Electron Flow ◽  
Current Model ◽  
Cyclic Electron Flow ◽  
Redox Activity ◽  
Cytochrome B6f Complex ◽  
Cytochrome B6f ◽  
Q Cycle ◽  
B6f Complex

Proton gradient regulation 5 (PGR5) is involved in the control of photosynthetic electron transfer, but its mechanistic role is not yet clear. Several models have been proposed to explain phenotypes such as a diminished steady-state proton motive force (pmf) and increased photodamage of photosystem I (PSI). Playing a regulatory role in cyclic electron flow (CEF) around PSI, PGR5 contributes indirectly to PSI protection by enhancing photosynthetic control, which is a pH-dependent down-regulation of electron transfer at the cytochrome b6f complex (b6f). Here, we re-evaluated the role of PGR5 in the green alga Chlamydomonas reinhardtii and conclude that pgr5 possesses a dysfunctional b6f. Our data indicate that the b6f low-potential chain redox activity likely operated in two distinct modes — via the canonical Q cycle during linear electron flow and via an alternative Q cycle during CEF, which allowed efficient oxidation of the low-potential chain in the WT b6f. A switch between the two Q cycle modes was dependent on PGR5 and relied on unknown stromal electron carrier(s), which were a general requirement for b6f activity. In CEF-favoring conditions, the electron transfer bottleneck in pgr5 was the b6f, in which insufficient low-potential chain redox tuning might account for the mutant pmf phenotype. By attributing a ferredoxin-plastoquinone reductase activity to the b6f and investigating a PGR5 cysteine mutant, a current model of CEF is challenged.

scholarly journals Electron transfer via cytochrome b6f complex displays sensitivity to Antimycin A upon STT7 kinase activation.

2022 ◽  
Author(s):  
Felix Buchert ◽  
Martin Scholz ◽  
Michael Hippler
Keyword(s):  
Electron Transfer ◽  
Electron Flow ◽  
Anaerobic Treatment ◽  
State Transitions ◽  
Antimycin A ◽  
Cytochrome B6f Complex ◽  
Cytochrome B6f ◽  
Q Cycle ◽  
B6f Complex

The cytochrome b6f complex (b6f) has been initially considered as the ferredoxin-plastoquinone reductase (FQR) during cyclic electron flow (CEF) with photosystem I that is inhibited by antimycin A (AA). The binding of AA to the b6f Qi-site is aggravated by heme-ci, which challenged the FQR function of b6f during CEF. Alternative models suggest that PROTON GRADIENT REGULATION5 (PGR5) is involved in a b6f-independent, AA-sensitive FQR. Here, we show in Chlamydomonas reinhardtii that the b6f is conditionally inhibited by AA in vivo and that the inhibition did not require PGR5. Instead, activation of the STT7 kinase upon anaerobic treatment induced the AA sensitivity of b6f which was absent in stt7-1. However, a lock in State 2 due to persisting phosphorylation in the phosphatase double mutant pph1;pbcp did not increase AA sensitivity of electron transfer. The latter required a redox poise, supporting the view that state transitions and CEF are not coercively coupled. This suggests that the b6f-interacting kinase is required for structure-function modulation of the Qi-site under CEF favoring conditions. We propose that PGR5 and STT7 independently sustain AA-sensitive FQR activity of the b6f. Accordingly, PGR5-mediated electron injection into an STT7-modulated Qi-site drives a Mitchellian Q cycle in CEF conditions.

scholarly journals Cytochrome b6f complex inhibition by antimycin-A requires Stt7 kinase activation but not PGR5

2020 ◽  
Author(s):  
Felix Buchert ◽  
Michael Hippler
Keyword(s):  
Electron Transfer ◽  
Electron Flow ◽  
Proton Gradient ◽  
Antimycin A ◽  
Cytochrome B6f Complex ◽  
Independent Manner ◽  
Cytochrome B6f ◽  
Kinase Activation ◽  
Site Function ◽  
B6f Complex

AbstractFerredoxin-plastoquinone reductase (FQR) activity during cyclic electron flow (CEF) was first ascribed to the cytochrome b6f complex (b6f). However, this was later dismissed since b6f inhibition by antimycin-A (AA) could not be reproduced. AA presumably fails to ligate with haem bh, at variance with cytochrome bc1 complex, owing to a specific Qi-site occupation in b6f. Currently, PROTON GRADIENT REGULATION5 (PGR5) and the associated PGR5-Like1 are considered as FQR in the AA-sensitive CEF pathway. Here, we show that the b6f is conditionally inhibited by AA in a PGR5-independent manner when CEF is promoted. AA inhibition, demonstrated by single b6f turnover and electron transfer measurements, coincided with an altered Qi-site function which required Stt7 kinase activation by a strongly reduced plastoquinone pool. Thus, PGR5 and Stt7 were necessary for b6f activity and AA-sensitive electron transfer in CEF-favouring conditions. Extending previous findings, a new FQR activity model of the b6f is discussed.

The cytochrome b6f complex. Novel aspects

1997 ◽  
Vol 100 (4) ◽  
pp. 852-862 ◽  
Author(s):  
William A. Cramer ◽  
Glenda M. Soriano ◽  
Huamin Zhang ◽  
Michael V. Ponamarev ◽  
Janet L. Smith
Keyword(s):  
Cytochrome B6f Complex ◽  
Cytochrome B6f ◽  
B6f Complex

Structure of the cytochrome b6f complex: new prosthetic groups, Q-space, and the ‘hors d’oeuvres hypothesis’ for assembly of the complex

2005 ◽  
Vol 85 (1) ◽  
pp. 133-143 ◽  
Author(s):  
William A. Cramer ◽  
Jiusheng Yan ◽  
Huamin Zhang ◽  
Genji Kurisu ◽  
Janet L. Smith
Keyword(s):  
Cytochrome B6f Complex ◽  
Cytochrome B6f ◽  
Prosthetic Groups ◽  
B6f Complex

An atypical haem in the cytochrome b6f complex

Nature ◽  
2003 ◽  
Vol 426 (6965) ◽  
pp. 413-418 ◽  
Author(s):  
David Stroebel ◽  
Yves Choquet ◽  
Jean-Luc Popot ◽  
Daniel Picot
Keyword(s):  
Cytochrome B6f Complex ◽  
Cytochrome B6f ◽  
B6f Complex

scholarly journals HCF164 Encodes a Thioredoxin-Like Protein Involved in the Biogenesis of the Cytochrome b6f Complex in Arabidopsis

2001 ◽  
Vol 13 (11) ◽  
pp. 2539-2551 ◽  
Author(s):  
Katja Lennartz ◽  
Henning Plücken ◽  
Andreas Seidler ◽  
Peter Westhoff ◽  
Nicole Bechtold ◽  
...  
Keyword(s):  
Cytochrome B6f Complex ◽  
Cytochrome B6f ◽  
B6f Complex

Cytochrome b6f Complex

2004 ◽  
pp. 521-527 ◽  
Author(s):  
Günter A. Hauska ◽  
Thomas Schödl
Keyword(s):  
Cytochrome B6f Complex ◽  
Cytochrome B6f ◽  
B6f Complex
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