Chlorophyll-Derivative Modulation of Rhodopsin Signaling Properties through Evolutionarily Conserved Interaction...

Area of Science:

• Biochemistry
• Molecular Biology
• Evolutionary Biology

Background:

• Retinal is the chromophore activating visual pigments, with spectral tuning adapting its light absorption.
• Dragon fish may utilize chlorophyll derivatives for photosensitization, an alternative to evolutionary spectral tuning.
• Understanding these mechanisms is crucial for visual pigment and G-protein coupled receptor (GPCR) research.

Purpose of the Study:

• To investigate the interaction between chlorophyll derivative chlorin-e6 (Ce6) and rhodopsin.
• To elucidate how Ce6 binding affects rhodopsin's spectral characteristics and dynamics.
• To explore the potential implications for G-protein coupled receptor class A (GPCR-A) function.

Main Methods:

• Experimental measurements of retinal-receptor interactions in rhodopsin.
• Computational modeling to probe Ce6 binding and its allosteric effects.
• Analysis of long-range correlated fluctuations and receptor dynamics.

Main Results:

• Chlorin-e6 (Ce6) binding in the intracellular domain (ICD) allosterically excites conserved long-range correlated fluctuations in GPCR-A.
• Ce6 binding modulates amino acid interactions in the retinal pocket, affecting spectral sensitivity (λmax).
• Ce6 alters rhodopsin's thermal stability and intrinsic conformational equilibrium via hydrogen-bonding adjustments.

Conclusions:

• Chlorophyll derivative binding can allosterically regulate GPCR-A receptor dynamics and function.
• This mechanism offers an alternative to traditional spectral tuning in visual systems.
• The observed allosteric effects may be conserved across all class A GPCRs due to conserved ICD residues and activation mechanisms.