Figure 6.

Effect of GTP, ATP, and zinc ions on D1 protein degradation in photoinactivated PSII core complexes. (A) Extent of D1 protein degradation determined by Western blotting. Isolated PSII core complexes were photoinactivated for 45 min at −1°C and subsequently incubated in darkness for 90 min in the absence and presence of 0.2 mM GTP or GTP[γS]. (B) Levels of the 23-kDa D1 fragment determined in samples of PSII core complexes, treated as in A, incubated in the absence and in the presence of 0.2 mM GTP or 1 mM ATP and 0.5 mM zinc acetate.