Protein clock dating
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 .This enzyme adds a few atoms to the neurotransmitter serotonin, then a second enzyme converts it into melatonin.That means that the two DNA versions differ by 100 million years of evolution and that their common ancestor lived 50 million years ago.Since each lineage experienced its own evolution, the two species must have descended from a common ancestor that lived at least 50 million years ago.
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.
It acts as our central pacemaker, checking the cycles of light and dark outside, and then sending signals to synchronize clocks throughout the rest of the body.
Molecular processes occur so fast that is it difficult to imagine a 24-hour clock that works at the molecular level.
To explore this structure in more detail, click on the image for an interactive JSmol. Goodsell (The Scripps Research Institute and the RCSB PDB) presents short accounts on selected molecules from the Protein Data Bank.
Each installment includes an introduction to the structure and function of the molecule, a discussion of the relevance of the molecule to human health and welfare, and suggestions for how visitors might view these structures and access further details.
For the first day or two, you experience jet lag because your clock is synchronized with the old schedule.