Virtuelle (Nano) Welten PDB Molecule of the Month 97: Circadian Clock Proteins

Sleepy Molecules

The small hormone melatonin is produced selectively at night, and circulates through the blood to coordinate our nightly activities, such as sleep. Treatment with melatonin may be used to change this cycle artificially, for instance helping to shift cycles that are out of phase during jet lag. The daily rise and fall of melatonin is caused by changes in the levels of the enzyme serotonin N-acetyltransferase, shown here from PDB entry 1cjw. This enzyme adds a few atoms to the neurotransmitter serotonin, then a second enzyme converts it into melatonin. In this structure, the enzyme is caught in the process of performing the reaction--the large green molecule bound in the active site is similar to the intermediate formed as the acetyl group is added to serotonin.