Quantification of photosystem I and II in different parts of the thylakoid membrane from spinach.
Electron paramagnetic resonance (EPR) was used to quantify Photosystem I (PSI) and PSII in vesicles originating from a series of well-defined but different domains of the thylakoid membrane in spinach prepared by non-detergent techniques. Thylakoids from spinach were fragmented by sonication and separated by aqueous polymer two-phase partitioning into vesicles originating from grana and stroma lamellae. The grana vesicles were further sonicated and separated into two vesicle preparations originating from the grana margins and the appressed domains of grana (the grana core), respectively. PSI and PSII were determined in the same samples from the maximal size of the EPR signal from P700(+) and Y(D)( .-), respectively. The following PSI/PSII ratios were found: thylakoids, 1.13; grana vesicles, 0.43; grana core, 0.25; grana margins, 1.28; stroma lamellae 3.10. In a sub-fraction of the stroma lamellae, denoted Y-100, PSI was highly enriched and the PSI/PSII ratio was 13. The antenna size of the respective photosystems was calculated from the experimental data and the assumption that a PSII center in the stroma lamellae (PSIIbeta) has an antenna size of 100 Chl. This gave the following results: PSI in grana margins (PSIalpha) 300, PSI (PSIbeta) in stroma lamellae 214, PSII in grana core (PSIIalpha) 280. The results suggest that PSI in grana margins have two additional light-harvesting complex II (LHCII) trimers per reaction center compared to PSI in stroma lamellae, and that PSII in grana has four LHCII trimers per monomer compared to PSII in stroma lamellae. Calculation of the total chlorophyll associated with PSI and PSII, respectively, suggests that more chlorophyll (about 10%) is associated with PSI than with PSII.
Danielsson
Ravi
R
Department of Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, S-22100 Lund, Sweden.
Albertsson
Per-Ake
PA
Mamedov
Fikret
F
Styring
Stenbjörn
S
D002734:Chlorophyll / Q000032:analysis; D004578:Electron Spin Resonance Spectroscopy; D045331:Photosystem I Protein Complex / Q000032:analysis* / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000032:analysis* / Q000737:chemistry; D018724:Spinacia oleracea / Q000737:chemistry*; D020524:Thylakoids / Q000737:chemistry* / Q000648:ultrastructure
D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll