Redox state of the Stt7 kinase does not change under high light. A, The redox state of Stt7 of Chlamydomonas cells transferred from low light to high light (950 µmol photons m-2s−1) was determined using mPEG-MAL at different time points as described in Fig. 2B. Cells in state 1 (ST1) and under prolonged anaerobiosis (AN, 60 min) were used as control. The number of Cys that reacted with mPEG-MAL is indicated on the right; mPM-, mPEG-MAL treatment was omitted. B, Same as A except that cells from three mutant Stt7 kinases, Stt7-Δ3Cys, Stt7- Δ Cys1 (Cys68Ala), Stt7- Δ Cys2 (Cys70Ala), were used. In Stt7- D3Cys the three non-conserved Cys within the catalytic domain were changed: C293L, C308I and C387I. HL, high light treatment.