RUTHENIUM RED INHIBITION OF OXYGEN EVOLUTION AND SPECIFIC RELEASE OF THE EXTRINSIC 16 kDa POLYPEPTIDE IN A PHOTOSYSTEM II PREPARATION

Abstract

The inhibitory effect of the dye ruthenium red was studied in photosystem II-enriched submembrane fractions. A number of distinct types of interaction were found, which differed in their concentration range and required incubation time. Ruthenium red instantaneously quenches the initial chlorophyll a fluorescence level (F ) and the maximum fluorescence level (F ) by enhancing radiationless deactivation in the chlorophyll light harvesting complex. Associated with this quenching of fluorescence is an instantaneous decrease in the quantum yield of oxygen evolution. Ruthenium red also inhibited the light saturated rate of oxygen evolution and the variable fluorescence, monitored 80 µs after a saturating excitation-flash. These inhibitions increased with incubation time and became greater than 50% within 5 min. Although ruthenium red was known to affect Ca or Cl sites specifically, the inhibitory action was more pronounced than simple Ca or Cl depletion. Incubation with ruthenium red for 5 min blocks the Z P680 → Z P680 charge transfer reaction. Upon mixing with the photosystem II preparation, ruthenium red induced specific release of the extrinsic 16 kDa polypeptide associated with water-splitting without release of Mn. It is proposed that the inhibitor produces an ionic imbalance which alters the configuration of the donor side of photosystem II.

Disorganization of the Mn4Ca complex of photosystem II by ruthenium red: a thermoluminescence study

“…4 demonstrates that the oscillation pattern is not significantly affected by RR, but also the amplitude of the TL signal obtained after each flash was declined in proportion to RR concentration. It was shown previously that the extrinsic polypeptide of 17 kDa is removed in the presence of RR (27) proteins, oxygen evolution is nearly lost, whereas the B-band emission can still be completely observed. Although PS II depleted of the extrinsic proteins exhibits normal oscillation up to the S 3 state, the final S 3 to S 0 transition that releases molecular oxygen is blocked (6).…”

“…In conclusion, RR is likely to disturb the Mn 4 Ca complex as it reaches the Ca 2+ site, which is consistent with RR being an inhibitor of Ca 2+ channels. Then, the absence of Mn release in the presence of RR (27) together with the inhibition of S 1 to S 2 state advancement shows that RR disorganizes the Mn cluster and thus impairs the reduction of Y Z . …”

“…From this, it has been suggested that the positive charge of RR is important for the efficiency of inhibition. In relation to the Ca 2+ binding site in the OEC, RR was shown to inhibit oxygen evolution and to release Ca 2+ and Cl − ions together with the 17 kDa polypeptide in PS II submembrane fractions (27). However, PS II electron transfer was restored if Cl − and Ca 2+ were provided in the reaction medium (28).…”

Inhibition of Oxygen Evolution in Chloroplast Photosystem Ii by the Protein‐modifying Agent Tetranitromethane

“…26 It was deduced that the interaction of ruthenium red at Ca2+ sites on the PSII polypeptides of 16 and 24 kDa or on their anchor proteins produces a conformational change that prevents their proper interaction with the membrane. 23 The modification of -SH groups and/or tyrosine residues by TNM could produce a similar conformational effect that would explain the removal of extrinsic polypeptides with consequent inhibition of electron transport.…”