Over-oxidation of the Alr4641 protein in
PCC7120. (A) Treatment with oxidative stress-inducing agents. Exponential phase cultures of Anabaena PCC7120 (3.0 μg chlorophyll a ml−1) were exposed to methyl viologen, (MV), hydrogen peroxide, (H2O2) or t-butyl hydroperoxide, (t-Bx) for 30 min. Cell free extracts (25 μg protein per lane) were resolved on non-reducing SDS-polyacrylamide gel, electroblotted onto a nitrocellulose membrane and probed with the Alr4641 antiserum. The dimeric (non-over-oxidized) form and the monomeric (oxidized) form are indicated in the figure. (B) Over-oxidation of Alr4641 in response to gamma (γ) radiation. Exponential phase cultures of Anabaena PCC7120 (6.0 μg chlorophyll a ml−1) were exposed to different doses of γ-radiation as indicated in the figure. The Alr4641 protein was detected immediately after irradiation as described in A. (C) After exposure to 6 kGy dose of γ-radiation, Anabaena cells were incubated in BG11N+ medium for recovery from radiation stress. Cells were removed at time points indicated and the Alr4641 protein was detected as before.