Figure 7.

Segregation of D1 and FtsH Protease in stn8 and stn7xstn8 Thylakoids.

(A) Immunoblot analysis of PsaA, PsaF, D1, and FtsH proteins in grana and stroma membranes fractionated by digitonin treatment and differential centrifugation of thylakoids from wild-type, stn8-1, stn8-2, and stn7xstn8 plants. Equal amounts of chlorophyll were loaded on each lane.

(B) Immunoblot analysis of D1 protein degradation in grana and stroma membranes fractionated by digitonin treatment of thylakoids from leaves of wild-type and stn7xstn8 plants treated with lincomycin and exposed to high light of 900 μmol photons m⁻² s⁻¹ during 0 or 3 h, as indicated.

(C) Immunoblot analysis of distribution of the D1 and PsaA proteins between the grana and stroma thylakoid membranes isolated from leaves of wild-type, stn8-1, stn8-2, and stn7xstn8 plants harvested in darkness or exposed for 3 h to normal light of 120 μmol photons m⁻² s⁻¹ or to high light of 900 μmol photons m⁻² s⁻¹.

(D) Time dependence of gravity-driven sedimentation of thylakoids isolated from wild-type and stn7xstn8 plants and resuspended in buffer with 5 mM MgCl₂ (+MgCl₂) or without MgCl₂ (−MgCl₂).

(E) Immunoblot analysis of D1 proteolysis in thylakoids isolated from wild-type and stn7xstn8 plants and resuspended in a buffer with 5 mM MgCl₂ (+MgCl₂) or without MgCl₂ (−MgCl₂) and supplied with 0.15 mM ZnCl₂ and 2 mM ATP. Immunoblotting was done using specific antibodies against the D1 and FtsH proteins, as indicated.

(F) Time-dependent proteolysis of D1 in thylakoids isolated from wild-type and stn7xstn8 plants and resuspended in buffer with 5 mM MgCl₂ (+MgCl₂) or without MgCl₂ (−MgCl₂) and supplied with 0.15 mM ZnCl₂ and 2 mM ATP. The values are mean ± se of three independent experiments for each experimental condition.

[See online article for color version of this figure.]