Proteins don’t get a lot of publicity, at least not compared with their glamour-puss cousins DNA and RNA. DNA, ensconced deep in the nucleus of cells, is the fountainhead, the living library of genes that embodies the very blueprints of life. And DNA begets RNA, the intrepid genetic messenger, braving the wilds of the cell to deliver DNA’s instructions to outlying factories that translate the blueprints into building materials-- that is, into proteins. Proteins just do all the work: they assemble, modify, and maintain the cells. True, without the efforts of these blue- collar laborers there would be no life at all, but proteins seem to lack the flash that has made heroes of their genetic kin.
But at last proteins are coming into their own. Proteins are amazing and subtle, says Peter S. Kim of the Whitehead Institute for Biomedical Research and the Howard Hughes Medical Institute at MIT. They’re finely tuned machines. I try to understand how they do the marvelous things they do.
Kim is not alone. His field of protein biology is flourishing as never before. Kim himself--at 37, he’s one of the field’s hottest young stars--has not only made discoveries that illuminate the fundamental nature of proteins and their relationship to diseases but has also identified an intriguing protein mechanism that may explain how viruses like flu and HIV manage to work their way into our cells. In doing so, Kim has perhaps provided a key for stopping those viruses in their tracks. The secret lies in the shapes proteins take when they fold.
Protein folding is one of the marvels of nature. When proteins roll off the cell’s assembly lines, they are nothing more than long chains of amino acids. Amino acids come in 20 varieties, and proteins typically contain between 100 and 10,000 amino acids. The acids function as a kind of alphabet, spelling out the form and function of the protein. Just as the 26 letters in the English alphabet can be arranged to spell a mind-boggling collection of words, the 20 amino acids combine to form tens of millions of proteins across the range of organisms on Earth. The human body alone contains some 50,000 kinds; among the structures they’re responsible for are muscle, skin, hair, cartilage, antibodies, enzymes, and hormones, to name just a few.