Heterogeneity of the Functional Antenna Size of Photosystem I from Spinach Thylakoids
We have recently fractionated the thylakoid membrane from spinach chloroplasts into two well separated vesicle populations (1). This was achieved by sonication and aqueous two-phase partitioning. A counter-current distribution diagram after such a fractionation is shown in Fig.1. The left peak comprises the grana derived α-vesicles while the right peak comprises the stroma derived β-vesicles. In this study we focused on examining the light harvesting properties of PSI of the two vesicle populations (PSIα and PSIβ respectively). We find different functional antenna sizes of PSI. PSIα has an antenna size about 30% larger than PSIβ. Our results imply that this heterogeneity in antenna size reflects the situation in the thylakoid membrane in vivo and is not due to any spill-over from PSII.
KeywordsThylakoid Membrane 120S Fraction Antenna Size Granum Membrane Spinach Thylakoid
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