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

Published online by Cambridge University Press:  10 September 2001

JIAN-XING MA ,
MASAHIRO KONO ,
LIN XU ,
JOYDIP DAS ,
JAMES C. RYAN ,
E. STARR HAZARD ,
DANIEL D. OPRIAN  and
ROSALIE K. CROUCH
JIAN-XING MA
Affiliation:
Department of Ophthalmology, Medical University of South Carolina, Charleston
MASAHIRO KONO
Affiliation:
Department of Biochemistry and the Volen Center for Complex Systems, Brandeis University, Waltham
LIN XU
Affiliation:
Department of Ophthalmology, Medical University of South Carolina, Charleston
JOYDIP DAS
Affiliation:
Department of Ophthalmology, Medical University of South Carolina, Charleston
JAMES C. RYAN
Affiliation:
Department of Ophthalmology, Medical University of South Carolina, Charleston
E. STARR HAZARD
Affiliation:
Department of Ophthalmology, Medical University of South Carolina, Charleston
DANIEL D. OPRIAN
Affiliation:
Department of Biochemistry and the Volen Center for Complex Systems, Brandeis University, Waltham
ROSALIE K. CROUCH
Affiliation:
Department of Ophthalmology, Medical University of South Carolina, Charleston
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Abstract

The visual pigment from the ultraviolet (UV) cone photoreceptor of the tiger salamander has been cloned, expressed, and characterized. The cDNA contains a full-length open reading frame encoding 347 amino acids. The phylogenetic analysis indicates that the highest sequence homology is to the visual pigments in the S group. The UV opsin was tagged at the carboxy-terminus with the sequence for the 1D4 epitope. This fusion opsin was expressed in COS-1 cells, regenerated with 11-cis retinal (A1) and immuno-purified, yielding a pigment with an absorbance maximum (λmax) of 356 nm which is blue shifted from the absorption of retinal itself. The transducin activation assay demonstrated that this pigment is able to activate rod transducin in a light-dependent manner. Regeneration with 11-cis 3,4-dehydroretinal (A2) yielded a pigment with a λmax of 360 nm, only 4 nm red shifted from that of the A1 pigment, while bovine rhodopsin generated with A2 showed a 16-nm red shift from the corresponding A1 pigment. These results demonstrate that the trend for a shorter wavelength pigment to have a smaller shift of λmax between the A1 and A2 pigments also fits UV pigments. We hypothesize that the small red shift with A2 could be due to a twist in the chromophore that essentially isolates the ring double bond(s) from conjugation with the rest of the polyene chain.

Keywords

AbsorbanceAmphibiansConeOpsinPhotoreceptorRetinaSalamanderUltravioletVisual pigment
Type
Research Article
Information
Visual Neuroscience , Volume 18 , Issue 3 , May 2001 , pp. 393 - 399
Copyright
2001 Cambridge University Press

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