Figure 5.

Protein Distribution and Phycobilin Levels in FtsH1down under N Depletion.

Cells of FtsH1down and the respective wild-type control (WT) were exposed for 24 h to N-deplete conditions (‒N) or grown for another 24 h under N-replete conditions (+N).

(A) Protein complexes isolated from +N/‒N cells were analyzed by 2D CN/SDS-PAGE. The 2D gel was stained with Sypro Orange and used for immunodetection with specific antibodies against NctA and P_II. White arrows indicate Amt1; the identity of Amt1 was verified by MS by Linhartová et al. (2014). Black arrows point to a shift in P_II migration in the SDS gel, likely due to different phosphorylation states in the WT − N. NtcA was not detectable by immunodetection under N+. Other designations: ATP. synt., AtpA/B subunits of ATP synthase; NtcA deg., putative degradation product of NtcA; 1 to 4, different P_II distribution in the CN direction. Each loaded membrane fraction sample contained 5 µg of chlorophyll a.

(B) Whole-cell absorption spectra were measured with cell suspensions of the same OD₇₅₀ of 0.1. Absorbance at the phycobilin peak maximum (620 nm), indicated by the solid line, reflects the level of phycobiliproteins in the cell. rel.u., relative units.