TY - JOUR
T1 - Bicarbonate-reversible formate inhibition at the donor side of photosystem II
AU - Wincencjusz, Hanna
AU - Allakhverdiev, Suleyman I.
AU - Klimov, Vyacheslav V.
AU - Van Gorkom, Hans J.
N1 - Funding Information:
Our findings show conclusively that in DT-20 membrane fragments the 4-step redox cycle of the oxygen evolving complex is blocked by submillimolar formate concentrations and that this effect is bicarbonate-reversible. It has been proposed that the formate inhibition discussed here is due to replacement of a bicarbonate ion essential for the binding of manganese in the oxygen-evolving complex \[4\]. Recent EPR measurements indicate that it is associated with the reversible release of one Mn(II) per PS II from the particles (Hulsebosch et al., unpublished data). It remains unclear why the proposed bicarbonate binding site is exposed (or created) only in the DT-20 preparation. This work was supported by the Netherlands Foundation for Chemical Research (SON) of the Netherlands Organization for Scientific Research (NWO), the INTAS foundation (Grant 93-2849), the International Science Foundation (Grant MTZ 000), and a EU DGXII Human Capital & Mobility Network Grant (CHRX-CT94-0524).
PY - 1996/1/11
Y1 - 1996/1/11
N2 - Flash-induced absorbance changes at 295 nm show that in the spinach Photosystem II preparation called DT-20 the four-step redox cycle of the oxygen evolving complex is blocked by very low formate concentrations, 50% at 10 μM, and fully restored by a 2-fold higher bicarbonate concentration. These concentrations are four orders of magnitude lower than those involved in the well-known acceptor-side inhibition by formate and did not affect 295 nm absorbance changes in thylakoids, 'BBY' PS II membrane fragments, or PS II core particles. The effect is not related to the chloride dependence of oxygen evolution and appears to be an all-or-none inhibition already present on the first flash.
AB - Flash-induced absorbance changes at 295 nm show that in the spinach Photosystem II preparation called DT-20 the four-step redox cycle of the oxygen evolving complex is blocked by very low formate concentrations, 50% at 10 μM, and fully restored by a 2-fold higher bicarbonate concentration. These concentrations are four orders of magnitude lower than those involved in the well-known acceptor-side inhibition by formate and did not affect 295 nm absorbance changes in thylakoids, 'BBY' PS II membrane fragments, or PS II core particles. The effect is not related to the chloride dependence of oxygen evolution and appears to be an all-or-none inhibition already present on the first flash.
KW - Bicarbonate
KW - Formate inhibition
KW - Oxygen evolution
KW - Photosystem II
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U2 - 10.1016/0005-2728(95)00136-0
DO - 10.1016/0005-2728(95)00136-0
M3 - Article
AN - SCOPUS:0030028014
SN - 0005-2728
VL - 1273
SP - 1
EP - 3
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 1
ER -