Figure 2.

Effect of chloroplast thioredoxins on the phosphorylation of LHCII and D1 proteins. Thylakoids isolated from dark-adapted leaves were incubated in darkness in the presence of thioredoxin f or m at the concentrations indicated. DTT (0.2 mM) was included in the incubation medium to keep thioredoxins in their reduced form. A minor effect of DTT on thylakoid protein phosphorylation (see Fig. 3) was always subtracted from the inhibition observed with thioredoxins. After incubation for 10 min in darkness, protein phosphorylation was initiated by the addition of ATP and turning the light on. Phosphorylation levels of proteins were detected as described in Fig. 1, and the blots were quantified by scanning. Results are means ± SD, n = 2.