Abstract
In higher plants, the photosynthetic process is performed and regulated by Photosystem II (PSII). Arabidopsis thaliana was the first higher plant with a fully sequenced genome, conferring it the status of a model organism; nonetheless, a high-resolution structure of its Photosystem II is missing. We present the first Cryo-EM high-resolution structure of Arabidopsis PSII supercomplex with average resolution of 2.79 Å, an important model for future PSII studies. The digitonin extracted PSII complexes demonstrate the importance of: the LHG2630-lipid-headgroup in the trimerization of the light-harvesting complex II; the stabilization of the PsbJ subunit and the CP43-loop E by DGD520-lipid; the choice of detergent for the integrity of membrane protein complexes. Furthermore, our data shows at the anticipated Mn4CaO5-site a single metal ion density as a reminiscent early stage of Photosystem II photoactivation.
Highlights
Photosynthesis is the most important natural process existing on our planet, in which solar radiation is converted into biomass[1,2]
The bacterial PSIIcc is expected to be very similar to the dimeric Photosystem II (PSII) core of higher plants (PSII C 2), there are several distinct d ifferences[31]: i. bacterial PSII lacks chlorophyll b; ii. the light-harvesting antenna is integrated into the membrane in higher plants, while it is peripheral in bacteria; iii. the extrinsic proteins differ between bacteria and higher plants; iv. the pigments and the lipids not always share conserved binding-sites between species of different kingdoms
We presented the first high-resolution structure of Photosystem II from wild-type Arabidopsis thaliana, allowing a detailed comparison to other higher plants’ PSII structures, while fairer comparison to existing high-resolution cyanobacterial PSII models
Summary
Photosynthesis is the most important natural process existing on our planet, in which solar radiation is converted into biomass[1,2]. Photosystem II reaction centre is built of the essential D1-D2 heterodimer, that hosts several cofactors responsible for the light-induced charge separation and water o xidation[6,8] These core proteins are connected to an internal core chlorophyll a binding antenna, composed of CP43 and CP47 p roteins[9]. The trimeric LHCII is the most abundant chlorophyll-binding protein assembly in eukaryotic photosynthetic organisms, and it is constituted of three polypeptides, Lhcb1Lhcb[1-312,13]. Several of these trimeric assemblies can bind simultaneously to a PSII core complex at specific locations. The bacterial PSIIcc is expected to be very similar to the dimeric PSII core of higher plants (PSII C 2), there are several distinct d ifferences[31]: i. bacterial PSII lacks chlorophyll b; ii. the light-harvesting antenna is integrated into the membrane in higher plants, while it is peripheral in bacteria (phycobilisomes); iii. the extrinsic proteins differ between bacteria and higher plants; iv. the pigments and the lipids not always share conserved binding-sites between species of different kingdoms
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