Figure 3.

Association of Ohp2 with PSI. A, Localization of Ohp2 in appressed and nonappressed regions of thylakoid membranes assayed by immunoblotting. As references, the distribution of subunits-A/B from the PSI reaction center (PSI-A/B) and the D1 protein from PSII (D1) reaction center were assayed. B, Location of Ohp2 in PSI. Thylakoid membranes isolated from control leaves grown under ambient light conditions (100 μmol m^–2 s^–1), were solubilized with n-dodecyl β-d-maltoside, and the released protein complexes were separated by a Suc density gradient centrifugation. The protein composition in collected fractions was analyzed on SDS-gel stained by Coomassie Blue (top). The distribution of PSI, PSII, and its antenna, cytochrome b/f, and ATP synthase complexes were analyzed by immunoblotting using polyclonal antibodies directed against the A and B subunits of PSI reaction center (PSI-A/B), the D1 protein of PSII reaction center, the chlorophyll a/b-binding protein of PSII (Lhcb2), the subunit f of the cytochrome b₆/f complex (cyt f), and the α-subunit of the CF1 ATP synthase complex (CF1-α; middle panels). Location of Ohp2 was assayed by immunoblotting (bottom). C, Composition of the fraction 11 tested by antibodies directed against subunits A, B, C, D, E, F, H, and L of PSI (PSI-A/B, PSI-D/F/L, or PSI-C/E/H, respectively), light-harvesting antenna proteins of PSI (Lhca1–4), and Ohp2.