**********
WHY DO PROTEINS "FOLD"?
However, only knowing this sequence tells us little about what the protein does and how it does it. In order to carry out their function (eg as enzymes or antibodies), they must take on a particular shape, also known as a "fold." Thus, proteins are truly amazing machines: before they do their work, they assemble themselves! This self-assembly is called "folding."
WHY IS PROTEIN FOLDING SO DIFFICULT TO UNDERSTAND?
It's amazing that not only do proteins self-assemble -- fold -- but they do so amazingly quickly: some as fast as a millionth of a second. While this time is very fast on a person's timescale, it's remarkably long for computers to simulate.
In fact, it takes about a day to simulate a nanosecond (1/1,000,000,000 of a second). Unfortunately, proteins fold on the tens of microsecond timescale (10,000 nanoseconds). Thus, it would take 10,000 CPU days to simulate folding -- i.e. it would take 30 CPU years! That's a long time to wait for one result!
While the nature of the fold is determined by the sequence, it is encoded in a very complicated manner. Thus, protein folding can be seen as a connection between the genome (sequence) and what the proteins actually do (their function).
