The rate of turnover of the cytochrome b6f complex
General Discussion
Andriy Herts, Nataliia Herts
May 2018
Hi. In the protocol RIDES, I see possibility measuring of "ATP synthase conductivity, proton motive force parameters through DIRK(ECS)" and "The rate of turnover of the cytochrome b6f complex through DIRKP(700)" Both based on Dark-interval relaxation kinetic (DIRK).
For estimate ATP synthase we have ECSt mAU, vH+, gH+ parameters in protocol and visualization setting through PhotosyQ-Web.
How kind of parameter directly is responsible for the estimate of turnover of the cytochrome b6f complex?
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May 2018
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David M. Kramer
May 2018
Hi Andriy and Nataliia!
Yes, this is possible. Some of the RIDES protocols takes two separate P700 traces. One is a DIRK (dark interval relaxation kinetics) using a short dark window during the steady state illumination. During this window, any P700+ (oxidized P700) will be reduced by electrons from b6f, though plastocyanin. The first-order decay constant for the reduction is related to the turnover rate of the b6f complex. There are some caveats to this, as described in one of our ancient papers (Sacksteder and Kramer, 2000, Photosynthesis Research 66, 145-158), but it should give you a pretty reasonable estimate of the rate of b6f turnover, and more importantly the process of "photosynthetic control".
over the next few days, I will work up an example project to demonstrate and let you know where to find it.
Bests,
Dave
David M. Kramer
May 2018
One more comment: In principle it should be possible to directly measure cytochrome f using a modified version of the MultispeQ. This would, however, require narrow band (monochromatic) measuring pulses using dichroic bandpass filters. We decided not to use these in the current versions of the MultispeQ because they would add a lot of cost to the device and, for the most part, the information can be obtained using the signals already available on the instrument.
Dave