Protein is a remarkable word and an even more remarkable part of the universe. Protein comes from the Greek word meaning "of first importance" -- and so it is, for without proteins, there would be no life.
Protein was the name suggested by that inveterate namer of organic compounds, the Swedish chemist Jöns Jakob Berzelius. The Dutch chemist Gerardus Johannes Mulder used Berzelius's suggestion in 1839 when he worked out a basic formula for what were then called "albuminous compounds", like egg white (casein) or blood globulin.
Carbohydrates and fats supply carbon, hydrogen, and oxygen (in various patterns), but proteins supply, in addition, nitrogen, sulphur, and often phosphorus. Proteins are complicated, and scientists are only now discovering the full extent of those complexities in the living cell.
Early methods of organic analysis were too crude to decipher the structure of proteins, but it was possible to analyze their building blocks of amino acids, which have a basic pattern of hydrogen and nitrogen atoms, a group of carbon, hydrogen, and oxygen atoms, and a branch group of atoms that identifies a particular amino acid.
After another Swedish chemist, Theodor Svedberg, invented the ultracentrifuge in 1923 (for which he received the Nobel Prize), scientists were able to determine the molecular weights of many proteins on the basis of their rate of sedimentation. The results were astonishing, for some proteins turned out to have molecular weights in the millions, indicating that their structure was exceedingly complex indeed.
Newer technology came along to help examine the structure of proteins -- nuclear magnetic resonance, chromatography, spectrophotometry, X-ray diffraction, and so on. It was found that in spite of the theoretically mammoth number of possible amino acids, proteins here on Earth contain only twenty varieties. It's quite possible [however,] that steak from another planet would not agree with a Terran.
For years, scientists believed that what they discovered about proteins in their test tubes was true of proteins in the living cell, but that turns out to have been a bit of hubris. Unanswered questions about cellular protein are keeping scientists busy, for it seems that proteins do not fold, spindle, or mutilate by themselves, They need help.
Folding is the key word. A protein's amino acid components have to be arranged correctly in order for the right doohickeys to be in the right place to do the right job. You can't have a nitrogen atom waggling off there when it should be here, up against something else. Mary-Jane Gething and Joseph Sambrook have described the fascinating functions of cellular proteins called "chaperones". These seem to exist in order to (1) help a complicated protein molecule fold properly, (2) stabilize partially folded intermediates or inactive proteins, (3) rearrange cellular macromolecules being assembled and disassembled, (4) protect proteins that are under environmental stress, and (5) pick out proteins for destruction.
All of this research may sound esoteric, but it's of vital importance. You are alive -- why not understand as much about life as possible? The new molecular biology research on proteins may make it possible to understand and cope with various diseases now incurable. There could be better medicines, designed to help cells heal themselves and to do no harm. Using chaperones, biotechnology might be able to produce important human proteins in quantities undreamed of now.
Proteins are also described as assembly line producers, as pumps for transfer, and as the engines that literally make life move. At a recent conference, the big question was -- how do protein machines use of the chemical energy? Some people think the trick is done by changing shape, but others disagree. Finding out the truth is tricky, since since it's necessary to make an inventory of the parts involved, identify the chemical intermediates of each reaction, measure the rate constants for the transitions, and describe the detailed structure of the protein to understand how the various chemical reactions are made to work. Not one of these steps is sufficiently known right now.
Biochemists and molecular biologists will continue their research on proteins so keep posted. When Freeman J. Dyson was asked which came came first in the evolution of life, proteins or DNA, he answered proteins.
Understanding those proteins will help humanity delve further into the mysteries not only of cellular pathology but of the origin of life itself.