Figure 2

Flash-induced raw polarographic transients recorded with a Clark-type O₂ electrode in C_i-free SMS buffer with PSII(Cah3-) membranes, blue symbols; PSII(Cah3-) membranes in the presence of 1 mM KHCO₃, green symbols and PSII(Cah3-) membranes reconstituted with 0.7 M recombinant Cah3 protein and 1 mM KHCO₃, red symbols. The lines result from simulations involving a delayed onset of the exponential rise, an either mono- or bi-exponential rise and an exponential decay. The following parameters were used in the simulations shown (delay//first rise time and amplitude//second rise time and amplitude//decay time): without additions (blue)—670 s//1.8 ms, 65%//6 ms, 35%//24 ms; with HCO₃ ^- (green)—600 s//1.8 ms, 84%//4 ms, 16%//24 ms; with HCO₃ ^- and Cah3 (red)—550 s//1.6 ms, 100%//not required//24 ms. Unless HCO₃ ^- and Cah3 are simultaneously supplemented, a bi-exponential simulation of the O₂ rise is required (see Supplementary data). However, due to extensive parameter correlations, various combinations of amplitudes and time constants can result in simulations of similar quality. A full-colour version of this figure is available at The EMBO Journal Online.