RESUMO
Pineal opsin (P-opsin), an opsin from chick that is highly expressed in pineal but is not detectable in retina, was cloned by the polymerase chain reaction. It is likely that the P-opsin lineage diverged from the retinal opsins early in opsin evolution. The amino acid sequence of P-opsin is 42 to 46 percent identical to that of the retinal opsins. P-opsin is a seven-membrane spanning, G protein-linked receptor with a Schiff-base lysine in the seventh membrane span and a Schiff-base counterion in the third membrane span. The primary sequence of P-opsin suggests that it will be maximally sensitive to approximately 500-nanometer light and produce a slow and prolonged phototransduction response consistent with the nonvisual function of pineal photoreception.
Assuntos
Proteínas do Tecido Nervoso/química , Glândula Pineal/química , Opsinas de Bastonetes/química , Sequência de Aminoácidos , Animais , Proteínas Aviárias , Sequência de Bases , Evolução Biológica , Química Encefálica , Galinhas , Clonagem Molecular , Dados de Sequência Molecular , Proteínas do Tecido Nervoso/análise , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/fisiologia , Estrutura Secundária de Proteína , RNA Mensageiro/análise , Retina/química , Opsinas de Bastonetes/análise , Opsinas de Bastonetes/genética , Opsinas de Bastonetes/fisiologia , Homologia de Sequência de AminoácidosRESUMO
We have previously shown that the level of [35S]methionine incorporation into tryptophan hydroxylase (TPH) shows a circadian rhythm in cultured chick pineal cells. The TPH protein oscillation persists in constant darkness, peaks in the early night and can be phase-shifted by light, in parallel to the effect of these treatments on melatonin synthesis. We have cloned and sequenced a full-length cDNA for chick pineal TPH. Levels of TPH mRNA show a robust diurnal oscillation both in vivo and in vitro. The rhythm in TPH mRNA also persists in constant darkness, suggesting that TPH mRNA synthesis and/or turnover is regulated by an endogenous circadian clock in cultured chick pineal cells. The circadian oscillation of TPH constitutes the first described circadian rhythm of a chick pineal gene at the mRNA level.