دانلود رایگان مقاله انرژی آنتن برداشت نور: بینش از جانب CP29

abstract

How do plants cope with excess light energy? Crop health and stress tolerance are governed by molecular photoprotective mechanisms. Protective exciton quenching in plants is activated by membrane energization, via unclear conformational changes in proteins called antennas. Here we show that pH and salt gradients stimulate the response of such an antenna under low and high energization by all-atom Molecular Dynamics Simulations. Novel insight establishes that helix-5 (H5) conformation in CP29 from spinach is regulated by chemiosmotic factors. This is selectively correlated with the chl-614 macrocycle deformation and interactions with nearby pigments, that could suggest a role in plant photoprotection. Adding to the significance of our findings, H5 domain is conserved among five antennas (LHCB1–5). These results suggest that light harvesting complexes of Photosystem II, one of the most abundant proteins on earth, can sense chemiosmotic gradients via their H5 domains in an upgraded role from a solar detector to also a chemiosmotic sensor/

5. Conclusions

Almost all energy of our ecosystem gets into the trophic pyramid via the light harvesting antenna of plants which switches rapidly, upon demand, between light harvesting and dissipative (i.e. protective quenching) conformations. It is widely accepted that ion gradients trigger conversion of the light harvesting conformation to dissipative conformation, but the exact sites are unknown and evidence is lacking. This hinders efforts to understand the biochemical regulation of this key nano-switch and the evolutionary pressure that acted on this gene family. In addition, it prevents us from maximizing crop yield and engineering more tolerant plants. In this work, we have presented several lines of evidence for conformational changes upon membrane energization in all-atom MD simulations of an antenna protein (CP29). Membrane energization is a common process in biochemistry that has been neglected in previous simulations of Light Harvesting Antenna. The work fundamentally changes our understanding of the response of CP29 in conditions of high membrane energization, giving novel insight into a sensor domain (helix-5, H5 or previously termed helix-D) that is able to detect chemiosmotic energization, as a new property for antenna proteins. A possible role and significance of the H5 sensor under NPQ conditions is only suggested, however excitation energy transfer studies in simulations of quantum nature will add towards this. The main scope of this study was to monitor conformational changes in LHC antenna under Non-Photochemical Quenching (NPQ) conditions. One might wonder how our work on CP29 relates to other antenna proteins. Although this work is focused on CP29 antenna, the key sensor domain (H5) identified is conserved among almost all antenna proteins of Photosystem II (namely LHCB1–5), that fine tune the balance between photosynthesis and photoprotection. Our findings will encourage and guide future works, like (a) mutagenesis experiments targeting residues at the lumen side for different LHCs, (b) a combination of computational simulations to address the extent of interplay between H5 motion and chlorophyll or carotenoid pigments, (c) bioinformatics studies that could detect energization sensitive domains in other genes, as well as (d) engineering of more tolerant plants and microalgae. Finally, our methodology simulating membrane energization opens up a new avenue to probe other chemiosmotic sensors in nature.