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Evaluation of Photosynthetic Behaviors by Simultaneous Measurements of Leaf Reflectance and Chlorophyll Fluorescence Analyses
Published on: August 9, 2019
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Feeling the Strain: Quantifying Ligand Deformation in Photosynthesis
Chientzu Lin1, Yuval Mazor2, Mike Reppert1
1Department of Chemistry, Purdue University, West Lafayette, Indiana 47920, United States.
The Journal of Physical Chemistry. B
|March 5, 2024
Summary
Structural distortion in chlorophyll proteins (CP) is hard to measure accurately from current structural data. While some ligand deformations are conserved, others vary too much for optical calculations.
Area of Science:
- Structural Biology
- Biophysics
- Biochemistry
Background:
- Protein-bound ligand structural distortion influences enzyme function by altering electronic and chemical properties.
- Quantifying these distortions is challenging due to limited protein structure resolution and difficulties in defining accurate restraints for non-protein ligands.
Purpose of the Study:
- To statistically quantify ligand distortion in chlorophyll proteins (CP), specifically focusing on ring deformation in photosystem II (PSII).
- To assess the reliability of ring deformation estimates from available structural data, particularly at resolutions down to 2 Å.
- To investigate the conservation of ring deformation across different species and the influence of refinement restraints.
Main Methods:
- Statistical analysis of ligand distortion in 113 distinct X-ray and cryogenic electron microscopy structures of photosystem II (PSII).
- Leveraging the C2 symmetry of PSII to compare ring deformation estimates for equivalent sites within and between structures.
- Evaluating the impact of refinement restraints on deformation values at resolutions as low as 2 Å.
Main Results:
- Significant variability was observed in several deformation modes, even for equivalent monomers at 2 Å resolution, potentially limiting their use in optical calculations.
- Refinement restraints critically influence deformation values, even at high resolutions (down to 2 Å).
- Well-resolved ring deformation modes in PSII are highly conserved across diverse species, from cyanobacteria to algae.
Conclusions:
- Structure-based analyses offer valuable insights into the bioenergetic and optical properties of chlorophyll proteins and other protein-ligand complexes.
- Limitations exist in current structural data resolution and refinement practices, impacting the accurate quantification of certain ligand distortions.
- Despite variability in some modes, conserved ring deformations in PSII highlight key structural features relevant to energy and electron transfer.
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