Salamander UV cone pigment: sequence, expression, and spectral properties

Area of Science:

• Vision science
• Molecular biology
• Photochemistry

Background:

• Cone photoreceptors are crucial for color vision.
• Ultraviolet (UV) visual pigments enable vision in the UV spectrum.
• Understanding visual pigment properties informs vision research.

Purpose of the Study:

• To clone, express, and characterize the UV cone visual pigment from the tiger salamander.
• To investigate the spectral properties and functional activity of the UV pigment.
• To compare the spectral shifts of UV pigments with A1 and A2 retinal forms.

Main Methods:

• cDNA cloning and expression in COS-1 cells.
• Regeneration of the opsin with 11-cis retinal (A1) and 11-cis 3,4-dehydroretinal (A2).
• Spectrophotometry to determine absorbance maximum (lambdamax) and transducin activation assays.

Main Results:

• The cloned UV opsin, when expressed and regenerated, formed a pigment with lambdamax of 356 nm (A1).
• The pigment activated rod transducin in a light-dependent manner.
• Regeneration with A2 resulted in a lambdamax of 360 nm, showing a smaller shift compared to bovine rhodopsin.

Conclusions:

• The tiger salamander UV visual pigment exhibits properties consistent with shorter wavelength pigments.
• The small spectral shift with A2 regeneration supports the hypothesis of chromophore twisting.
• This study provides insights into the molecular basis of UV vision and pigment spectral tuning.