A brand-new research study has actually exposed a quantum switching system in Light-harvesting complex II (LHCII), crucial for efficient photosynthesis. The Light-harvesting complex II (LHCII) consists of pigment particles connected to proteins. It alternates in between two primary roles: when under intense light, it dissipates excess energy as heat through nonphotochemical quenching, and under low light, it efficiently moves light to the response.
Comparison of these various structures reveals that LHCII undergoes a conformational modification upon acidification. Hence, LHCII confined with lateral pressure (e.g., aggregated LHCII) is a requirement for non-photochemical quenching (NPQ), whereas acid-induced conformational change enhances fluorescence quenching.
As part of their work, they reported a series of six cryo-EM structures, consisting of the energy transfer state with LHCII in option and the energy satiating state with laterally confined LHCII in membrane nanodiscs under both neutral and acidic conditions.
Comparison of these different structures shows that LHCII undergoes a conformational modification upon acidification. This modification allosterically modifies the inter-pigment distance of the fluorescence quenching locus Lutein1 (Lut1)– Chlorophyll612 (Chl612) only when LHCII is confined in membrane nanodiscs, leading to the quenching of thrilled Chl612 by Lut1. Therefore, LHCII restricted with lateral pressure (e.g., aggregated LHCII) is a requirement for non-photochemical quenching (NPQ), whereas acid-induced conformational change boosts fluorescence quenching.
Cryo-EM structures for LHCII in nanodisc and in cleaning agent service at pH 7.8 and 5.4. Credit: Institute of Physics
Quantum Switching Mechanism in Photosynthesis
Through MSDFT estimations of cryo-EM structures and the understood crystal structure in quenched states, together with transient fluorescence experiments, a considerable quantum switching system of LHCII has been revealed with Lut1– Chl612 range as the crucial element.
This range manages the energy transfer quantum channel in response to the lateral pressure on LHCII and the conformational change, that is, a slight change at its critical range of 5.6 Å would permit reversible switching between light harvesting and excess energy dissipation. This system makes it possible for a fast response to modifications in light intensity, ensuring both high performance in photosynthesis and balanced photoprotection with LHCII as a quantum switch.
The relationship in between fluorescence decay rate, Lut1– Chl612 electronic coupling strength against Lut1– Chl612 separation distance, and plot of Lut1– Chl612 distance versus the crossing angle of TM helices A and B in various LHCII structures. Credit: Institute of Physics
Formerly, these two research groups had actually collaborated on molecular dynamics simulations and ultrafast infrared spectroscopy experiments and had proposed that LHCII is an allosterically controlled molecular device. Their present experimental cryo-EM structures validate the previously in theory forecasted structural modifications in LHCII.
Reference: “Cryo-EM structures of LHCII in photo-active and photo-protecting states reveal allosteric policy of light harvesting and excess energy dissipation” by Meixia Ruan, Hao Li, Ying Zhang, Ruoqi Zhao, Jun Zhang, Yingjie Wang, Jiali Gao, Zhuan Wang, Yumei Wang, Dapeng Sun, Wei Ding and Yuxiang Weng, 31 August 2023, Nature Plants.DOI: 10.1038/ s41477-023-01500-2.
This research was supported by jobs from the Chinese Academy of Sciences, the National Natural Science Foundation of China, and the Shenzhen Municipal Science and Technology Innovation Commission.
A new study has revealed a quantum changing mechanism in Light-harvesting complex II (LHCII), important for effective photosynthesis. This discovery, accomplished through innovative cryo-EM and theoretical estimations, verifies LHCIIs dynamic role in managing energy transfer in plants. Credit: SciTechDaily.com
Photosynthesis is an essential process making it possible for plants to change co2 into organic compounds using sunlight. The Light-harvesting complex II (LHCII) consists of pigment particles connected to proteins. It rotates between two primary functions: when under intense light, it dissipates excess energy as heat through nonphotochemical quenching, and under low light, it efficiently transfers light to the reaction center.
Recent bioengineering research has revealed that accelerating the switch between these functions can boost photosynthetic effectiveness. Soybean crops have revealed yield increases of up to 33%. The precise atomic-level structural changes in LHCII that trigger this guideline were formerly unidentified.
Molecular system of NPQ and acidity-induced changes in some key structural factors drive the LHCII trimer to switch between light-harvesting and energy-quenching states. Credit: Institute of Physics
Ingenious Research Approach
ln a brand-new research study, researchers led by Prof. Weng Yuxiang from the Institute of Physics of the Chinese Academy of Sciences, together with Prof. Gao Jialis group from Shenzhen Bay Laboratory, integrated single-particle cryo-electron microscopy (cryo-EM) studies of vibrant structures of LHCII at atomic resolution with multistate density practical theory (MSDFT) calculations of energy transfer in between photosynthetic pigment molecules to recognize the photosynthetic pigment quantum switch for intermolecular energy transfer.
