Anti-OPN3 (C-terminal) polyclonal antibody

ks part of an ongoing search to identify novel mammalian photopigments that may mediate nonvisual tasks such as circadian entrainment and acute suppression of pineal melatonin levels, a number of recently cloned nonvisual opsin sequences were used to search dbEST, panopsin (OPN3) was one of the clones identified using this approach, Expression analysis detects two transcripts of approximately 2.1 and 2.5 kb, in a wide range of tissues including brain, liver, and retina, which encode a predicted protein of 403 amino acids. The gene was localized to the region of chromosome 1q43 also encompassing the kynurenine monooxygenase (KMO) and choroideremia-like Rab escort protein 2 (CHML) genes. KMO and panopsin overlap at their 3' ends but are transcribed in opposite directions, CHML, an intronless gene, lies in intron 1 of panopsin, (C) 2001 Academic Press.

Opn3/TMT opsins belong to one of the opsin groups with vertebrate visual and non-visual opsins, and are widely distributed in eyes, brains and other internal organs in various vertebrates and invertebrates. Vertebrate Opn3/TMT opsins are further classified into four groups on the basis of their amino acid identities. However, there is limited information about molecular properties of these groups, due to the difficulty in preparing the recombinant proteins. Here, we successfully expressed recombinant proteins of TMT1 and TMT2 opsins of medaka fish (Oryzias latipes) in cultured cells and characterized their molecular properties. Spectroscopic and biochemical studies demonstrated that TMT1 and TMT2 opsins functioned as blue light-sensitive Gi/Go-coupled receptors, but exhibited spectral properties and photo-convertibility of the active state different from each other. TMT1 opsin forms a visible light-absorbing active state containing all-trans-retinal, which can be photo-converted to 7-cis- and 9-cis-retinal states in addition to the original 11-cis-retinal state. In contrast, the active state of TMT2 opsin is a UV light-absorbing state having all-trans-retinal and does not photo-convert to any other state, including the original 11-cis-retinal state. Thus, TMT opsins are diversified so as to form a different type of active state, which may be responsible for their different functions.