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Updated: Dec 29, 2025
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Strategic Screening and Characterization of the Visual GPCR-mini-G Protein Signaling Complex for Successful Crystallization
Published on: March 16, 2020
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High-resolution structural insights into the heliorhodopsin family
K Kovalev1,2,3,4,5, D Volkov2,3, R Astashkin1,4
1Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-Commission for Atomic Energy (CEA)-CNRS, 38000 Grenoble, France.
Summary
Newly discovered heliorhodopsins (HeRs) possess unique structures distinct from known rhodopsins. Their unique cytoplasmic cavity suggests a role in fundamental biological processes, potentially enzymatic activity.
Area of Science:
- Structural Biology
- Biochemistry
- Microbiology
Background:
- Rhodopsins are abundant light-harvesting proteins.
- A novel family, heliorhodopsins (HeRs), has been identified with unique N-terminal orientation.
- The function of heliorhodopsins remains largely unknown.
Purpose of the Study:
- To elucidate the structure of bacterial heliorhodopsin-48C12 (HeR-48C12).
- To understand the structural differences between HeRs and known rhodopsins.
- To infer the potential function of HeRs based on structural insights.
Main Methods:
- X-ray crystallography to determine HeR-48C12 structures at 1.5 Å resolution.
- Bioinformatic analysis for HeR subfamily identification.
- Structural comparison with known rhodopsin families.
Main Results:
- Detailed structures of HeR-48C12 in two states reveal significant divergence from known rhodopsins.
- The extracellular region is hydrophobic; the cytoplasmic region contains a Schiff base cavity (SBC) with water molecules.
- At acidic pH, acetate was observed within the SBC.
- Bioinformatics identified 10 HeR subfamilies, indicating diverse functions.
Conclusions:
- HeR-48C12 exhibits a unique structural architecture.
- The SBC and its contents suggest a role as a proton acceptor.
- The HeR-48C12 subfamily may possess enzymatic activity and participate in redox processes.
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