Cloning and characterization of the pineal gland-specific opsin gene of marine lamprey (Petromyzon marinus)

We have cloned and sequenced the pineal gland-specific opsin (P opsin) gene, p(Pm), of marine lamprey, P. marinus. The deduced P opsin, P(Pm), consisting of 444 aa, is about 90 aa longer than the orthologous opsins of chicken, pigeon, and American chameleon. The evolution of P(Pm) is characterized not only by a significantly higher rate of aa replacement than the other P opsins but also by a larger number of unique aa replacements at highly conserved sites in the nonTM region. These changes in P(Pm) might have been important in achieving marine lamprey-specific interaction between P(Pm) and other proteins in the pineal gland.