| Budget Amount *help |
¥15,700,000 (Direct Cost: ¥15,700,000)
Fiscal Year 2006: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2005: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2004: ¥9,300,000 (Direct Cost: ¥9,300,000)
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| Research Abstract |
More than 2000 rhodopsins and their related photosensitive proteins (hereby referred to as rhodopsins), and they are divided into roughly 5 classes. This research was aimed at elucidating
1. relationship between molecular evolution of rhodopsins and counterion displacement from G1u181 to Glu113,
2. relationship between molecular properties of rhodopsins that have the Glu181 counterion and their cellular and physiological functions. The research results for three years as follows.
1. We successfully expressed varied rhodopsins in cultured cells and investigated their counterion by using site directed mutant proteins. We found that acquisition of Glull3 counterion resulted in acquisition of a higher G protein activation ability and red-sensitive cone pigment. Biochemical studies suggested that the higher G protein activation ability was due to a specialized conformational change of Glu113-counterion rhodopsin, compared with those of other rhodopsins.
2. We succeeded in expression of Glu181-c
… More
ounterion rhodopsins, namely parapinopsin, melanopsin and parietopsin. The biochemical, spectroscopic, histochemical and electrophysiological studies revealed the relationship between molecular properties of the rhodopsins and their physiological function as well as evolution of photoreception.
Cheracterization of the amphioxus melanopsin revealed that biochemical and photochemical properties, not just primary structure, of the melanopsin are considerably similar to those of the rhodopsins in the rhabdomeric visual cells of higher invertebrates. Taken together with the fact that the amphioxus melanopsin is expressed in the rhabdomeric photoreceptor cells, the cephalochordate rhabdomeric photoreceptor represents an evolutionary link between the vertebrate photosensitive ganglion cell and the invertebrate rhabdomeric visual cell.
Our molecular biological, histochemical and electorophysiological studies showed a UV pigment functioning in the lamprey pineal is the parapinopsin, which exhibits an absorption maximum at 370 nm. UV light causes a stable photoproduct having an absorption maximum at 515 nm, in the green region. The photoproduct reverts to the original pigment upon visible light absorption, showing photoregeneration of the pigment. The results demonstrated that parapinopsin is the pineal UV pigment having photo-interconvertible two stable states. The bistable nature of the parapinopsin can account for the photorecovery of the pineal UV-sensitivity by background green light in the lamprey.. Less
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