Molecular cloning of serotonin N-acetyltransferase gene from the mouse and its daily expression in the retina.

The primary structure of serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase, AA-NAT: the rate-limiting enzyme in melatonin synthesis) in the mouse retina was deduced from the cDNA nucleotide sequence. The deduced protein consisted of 205 amino-acid residues with sequences highly conserved in AA-NATs of vertebrates, and was 96% identical to rat AA-NAT. Northern blot analysis of mouse retinal mRNA showed two obvious bands, of 1.5 kb and 4.5 kb in length. The levels of both transcripts were low at day and high at night, but the night-to-day ratios were <2. These findings suggest that the expression mechanism of AA-NAT transcripts in the mouse retina may be different from those in other mammals, where a single transcript of AA-NAT is normally observed in Northern blots.