Table 1. Effect of light exposure at night on degree of phosphorylation of T31 and S205.

AANAT residue	Night (% )	Night + 30′ light pulse (% )	Light-induced change
T31	37.0 ± 2.4	25.4 ± 3.0	-11.6 ± 3.8*
S205	55.1 ± 2.9	35.2 ± 2.3	-19.9 ± 3.7*

Pineal glands were obtained during the night (0200 hours) or after a 30-min exposure to light at night (0230 hours); for each time, pools of two glands each were used to prepare supernatants. Samples of each supernatant were incubated with ATP and the catalytic subunit of PKA for 15 min at 20°C or without ATP and PKA for 0 min at 4°C. Proteins were resolved by SDS/PAGE; each gel contained a complete set of samples of unphosphorylated and phosphorylated night and night + light supernatants; results were normalized within a single blot and are presented as percent of T31 and S205 that is phosphorylated in AANAT obtained from pineal glands at night and at night after 30-min pulse of light.

^*The data are expressed as a mean ± SE (n = 5, P < 0.05). For further details see Materials and Methods and the Fig. 2 legend.