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Channel Rhodopsins

Channel Rhodopsins

Most organisms use photoreceptors to sense and respond to light. Examples of photoreceptors include bacteriorhodopsins and bacteriophytochromes in some bacteria, phytochromes in plants, and rhodopsins in the photoreceptor cells of the vertebral retina. The light-sensitive property of these receptors is because of the bound chromophores, such as bilin in the phytochromes and retinal in the rhodopsins.
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...

Evolution of New Traits in Microbes

Evolution of New Traits in Microbes

Microorganisms evolve rapidly due to their large population sizes and short generation times, often exhibiting measurable changes within days under laboratory conditions. Natural selection acts on standing genetic variation, enabling the retention and amplification of beneficial traits that confer fitness advantages in changing environments.Adaptive Pigment Regulation in RhodobacterIn Rhodobacter, a genus of purple non-sulfur bacteria, light-harvesting pigments such as bacteriochlorophyll and...

Photoreceptors and Visual Pathways

Photoreceptors and Visual Pathways

At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...

Gene Duplication and Divergence

Gene Duplication and Divergence

The seminal work of Ohno in 1970 popularized the idea of gene duplication and divergence. DNA sequence comparison studies reveal that a large portion of the genes in bacteria, archaebacteria, and eukaryotes was generated by gene duplication and divergence, indicating its critical role in evolution.
The duplicated copies of the gene are called Paralogs. Paralogs with similar sequences and functions form a gene family. Across several species, a large number of gene families are characterized.

Anoxygenic Photosynthesis

Anoxygenic Photosynthesis

Anoxygenic photosynthesis is a phototrophic process that captures light energy to drive carbon fixation without producing molecular oxygen. Unlike oxygenic photosynthesis, which utilizes water as an electron donor and releases oxygen, anoxygenic phototrophs use alternative electron donors such as hydrogen sulfide (H₂S), elemental sulfur (S⁰), or thiosulfate (S₂O₃²⁻). This process is carried out by diverse groups of bacteria, including purple bacteria, green sulfur bacteria, heliobacteria, and...

The Photochemical Reaction Center

The Photochemical Reaction Center

Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...

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Related Experiment Video

Updated: May 9, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Published on: June 27, 2014

Mechanism divergence in microbial rhodopsins.

John L Spudich¹, Oleg A Sineshchekov¹, Elena G Govorunova¹

¹Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Medical School, 6431 Fannin St., MSB6.130, Houston, TX 77030, USA.

Biochimica Et Biophysica Acta

|July 9, 2013

Summary

Microbial rhodopsins, like proton pumps and sensory rhodopsins, utilize light-induced conformational changes. Algal channelrhodopsins, however, exhibit unique proton transfer and channel gating mechanisms for phototaxis.

Keywords:

Microbial rhodopsins Optogenetics Photosensory transduction Phototaxis Proton transfer Schiff base connectivity

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Last Updated: May 9, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Published on: June 27, 2014

Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins

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Published on: October 4, 2024

Area of Science:

Biochemistry
Molecular Biology
Structural Biology

Background:

Microbial rhodopsins share a fundamental design principle of light-induced conformational changes between E (outwardly open) and C (cytoplasmically open) states.
Proton pumps and sensory rhodopsins (SRI, SRII) use these conformational changes and Schiff base proton transfers for vectorial proton transport or signal transduction.
Algal phototaxis receptors, such as channelrhodopsins, represent a distinct evolutionary path within microbial rhodopsins.

Purpose of the Study:

To review the diverse molecular functions evolved from the shared structure and chemistry of microbial rhodopsins.
To elucidate the unique mechanisms of algal phototaxis receptors (channelrhodopsins) in contrast to proton pumps and other sensory rhodopsins.
To understand how evolutionary modifications led to light-driven ion transport and photosensory signaling.

Main Methods:

Comparative analysis of photocycle intermediates and conformational transitions (E and C states) across different microbial rhodopsins.
Investigation of Schiff base proton transfer dynamics and channel gating mechanisms.
Review of structural and functional data on proton pumps, sensory rhodopsins, and channelrhodopsins.

Main Results:

Microbial rhodopsins generally undergo E→C or C→E transitions with vectorial proton transfer.
Sensory rhodopsins have evolved novel chemical processes altering conformational changes for signaling.
Channelrhodopsins exhibit redirected proton transfers and modified E→C transitions without external half-channel closure, enabling light-gated ion channel activity.

Conclusions:

The basic structure and chemistry of microbial rhodopsins have been diversely modified through evolution.
These modifications have led to distinct functions including light-driven ion transport and photosensory signaling.
Channelrhodopsins represent a unique adaptation for phototaxis, diverging from ancestral proton pump and sensory rhodopsin mechanisms.