πρωτεῖος

In 1838, Swedish chemist Jöns Jacob Berzelius received a letter from Dutch chemist Gerardus Mulder describing a mysterious substance found in all living things—in egg whites, in muscle, in blood. Mulder had isolated it but didn't know what to call it. Berzelius suggested the name protein, from Greek proteios meaning 'of the first quality' (from protos, 'first'). These molecules were primary; nothing worked without them.

Berzelius was thinking of Proteus, the shape-shifting sea god from Greek mythology. Proteus could transform into any form—water, fire, lion, tree. He was the god of transformation and adaptation. Proteins are shape-shifters too: they fold into thousands of configurations, each with a different purpose. A protein in blood vessels looks nothing like a protein in muscle, but they're all proteins.

For a century, scientists knew proteins were crucial to life but had no idea how they worked. In 1951, Linus Pauling discovered that proteins coiled into alpha-helices and beta-sheets. In 1958, Frederick Sanger won the Nobel Prize for sequencing a protein's amino acids. In 1968, Christian Anfinsen proved that the sequence of amino acids determined the shape a protein would fold into.

Now we know: proteins fold themselves. A string of amino acids emerging from a ribosome twists and turns and coils until it becomes an enzyme, a hormone, an antibody, a transport molecule. The same Greek word Berzelius used—protein, 'of first quality'—describes molecules that literally run every chemical reaction in your body.