Structure of a minimal photosystem I from the green alga Dunaliella salina.

Solar energy harnessed by oxygenic photosynthesis supports most of the life forms on Earth. In eukaryotes, photosynthesis occurs in chloroplasts and is achieved by membrane-embedded macromolecular complexes that contain core and peripheral antennae with multiple pigments. The structure of photosystem I (PSI) comprises the core and light-harvesting (LHCI) complexes, which together form PSI-LHCI.

Crystal Structure of Photosystem I Monomer From PCC 6803.

A single histidine addition to the C-terminus of PsaL of sp. PCC 6803 was previously reported by our lab to shift the trimer-to-monomer ratio of PSI in favor of the monomeric form. P700 re-reduction and NADP photo-reduction measurements of the PsaL strain show no effect on PSI activity in comparison to the WT trimeric PSI.

Structure and function of wild-type and subunit-depleted photosystem I in Synechocystis.

The ability of photosynthetic organisms to use the sun's light as a sole source of energy sustains life on our planet. Photosystems I (PSI) and II (PSII) are large, multi-subunit, pigment-protein complexes that enable photosynthesis, but this intriguing process remains to be explained fully. Currently, crystal structures of these complexes are available for thermophilic prokaryotic cyanobacteria.