Chimeric nature of pinopsin between rod and cone visual pigments

Atsushi Nakamura, Daisuke Kojima, Hiroo Imai, Akihisa Terakita, Toshiyuki Okano, Yoshinori Shichida, Yoshitaka Fukada

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Chicken pineal pinopsin is the first example of extra-retinal opsins, but little is known about its molecular properties as compared with retinal rod and cone opsins. For characterization of extra-retinal photon signaling, we have developed an overexpression system providing a sufficient amount of purified pinopsin. The recombinant pinopsin, together with similarly prepared chicken rhodopsin and green-sensitive cone pigment, was subjected to photochemical and biochemical analyses by using low-temperature spectroscopy and the transducin activation assay. At liquid nitrogen temperature (- 196°C), we detected two kinds of photoproducts, bathopinopsin and isopinopsin, having their absorption maxima (λ(max)) at 527 and ~440 nm, respectively, and we observed complete photoreversibility among pinopsin, bathopinopsin, and isopinopsin. A close parallel of the photoreversibility to the rhodopsin system strongly suggests that light absorbed by pinopsin triggers the initial event of cis-trans isomerization of the 11-cis- retinylidene chromophore. Upon warming, bathopinopsin decayed through a series of photobleaching intermediates: lumipinopsin (λ(max) 461 nm), metapinopsin I (460 nm), metapinopsin II (385 nm), and metapinopsin III (460 nm). Biochemical and kinetic analyses showed that metapinopsin II is a physiologically important photoproduct activating transducin. Detailed kinetic analyses revealed that the formation of metapinopsin II is as fast as that of a chicken cone pigment, green, but that the decay process of metapinopsin II is as slow as that of the rod pigment, rhodopsin. These results indicate that pinopsin is a new type of pigment with a chimeric nature between rod and cone visual pigments in terms of the thermal behaviors of the meta II intermediate. Such a long-lived active state of pinopsin may play a role in the pineal-specific phototransduction process.

Original languageEnglish
Pages (from-to)14738-14745
Number of pages8
JournalBiochemistry
Volume38
Issue number45
DOIs
Publication statusPublished - 1999 Nov 9
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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    Nakamura, A., Kojima, D., Imai, H., Terakita, A., Okano, T., Shichida, Y., & Fukada, Y. (1999). Chimeric nature of pinopsin between rod and cone visual pigments. Biochemistry, 38(45), 14738-14745. https://doi.org/10.1021/bi9913496