FIGURE 4.

Effect of high light on Anabaena and Synechocystis 2-Cys Prx overoxidation in vivo. A, cells grown to mid-exponential phase at 50 μE m⁻² s⁻¹ were diluted to a concentration of 2.5 μg of chlorophyll ml⁻¹ and exposed to a light intensity of 800 μE m⁻² s⁻¹. After 30 min of high light exposure, chloramphenicol (200 μg/ml final concentration) was added to one aliquot and incubated for a further 30 min (Cm). Cytosolic extracts of samples from Anabaena (5 μg of protein) and Synechocystis (25 μg of protein) harvested at the times indicated were subjected to SDS-PAGE under non-reducing conditions and Western blot analysis. The overoxidized form of the 2-Cys Prxs is distinguished as a monomer. Molecular mass markers, in kDa, are indicated on the left. mon, monomer; dim, dimer. B, extracts (15 μg of protein) from Anabaena cultures at the indicated times of high light treatment were subjected to two-dimensional gel electrophoresis and Western blot. Ox, overoxidized; Red, reduced.