Jen C. Skou | Biography

Jens Christian Skou was born October 8, 1918, in Lemvig, Denmark. He received his M.D. degree (cand. med.) from the University of Copenhagen in 1944. Ten years later, he received his Doctor of Medical Sciences degree (dr. med.) from Aarhus University.

After achieving his M.D., Skou went for clinical training at the Hospital at Hjørring and Orthopaedic Clinic at Aarhus, Denmark. He remained there until 1947, when he became an assistant professor in the University of Aarhus's Institute of Physiology. In 1954, he became associate professor at the Institute. In 1963 Skou became a full professor and was named chairman of the Institute of Physiology. From 1978 to 1988, he was professor of biophysics at the University of Aarhus.

Skou has devoted his career to both education and research. He has published more than 90 papers on his research, which has investigated the actions of local anesthetics and what mechanisms make them work, as well as the discovery that earned him the 1997 Nobel Prize for Chemistry, the transport of sodium and potassium ions through the cell membranes.

A cell's health depends on maintaining a balance between its inner chemistry and its surroundings. This balance is controlled by the presence of the cell membrane, the wall between the cell's inner workings and its environment.

For more than 70 years, scientists have known that one of the delicate balances that are maintained involves ions (electrically charged particles) of the elements sodium (Na) and potassium (K). A cell maintains its inner concentration of sodium ions (Na+) at a level lower than that of its surroundings. Similarly, it maintains its inner concentration of potassium ions (K+) at a level higher than its surroundings.

This balance is not static, however. In the 1950s, English researchers Alan Hodgkin and Richard Keynes found that sodium ions rush into a nerve cell when it is stimulated. After the stimulation, the cell restores its original sodium/potassium levels by transporting the extra sodium out through its membrane. Scientists suspected that this transport involved the compound adenosine triphosphate (ATP). Discovered in 1929, ATP was shown to carry energy in the cell. Scientists noticed that, when ATP's presence was inhibited, cells did not rid themselves of the extra sodium that they absorbed during stimulation.

In the 1950s, Skou began his investigations into the workings of ATP. For his experimental material he chose nerve membranes from crabs. He wanted to find out if there was an enzyme in the nerve membranes that degraded ATP and that could be involved with the transport of ions through the membrane.

He did find such an ATP-degrading enzyme, which needed ions of magnesium. In his experiments, Skou found that he could stimulate the enzyme by adding sodium ions--but there was a limit to the stimulation he could achieve. Adding small amounts of potassium ions, however, stimulated the enzyme even more. In fact, Skou noted that the enzyme--ATPase--reached its maximum point of stimulation when he added quantities of sodium and potassium ions that were the same as those normally found in nerve cells. This evidence made Skou hypothesize that the enzyme worked with an ion "pump" in the cell membrane.

Skou published his first paper on ATPase in 1957. In years of further experimentation, he learned more about this remarkable enzyme. He learned that different places on the enzyme attracted and bound ions of sodium and potassium.

When ATP breaks down and releases its energy, it become adenosine diphosphate (ADP) and releases a phosphate compound. Skou's work revealed that this freed phosphate bound to the ATPase as well, a process known as phosphorylation. The presence or absence of this phosphate changed the enzyme's interaction with sodium and potassium ions, Skou discovered. When the ATPase lacked a phosphate group, it becomes dependent on potassium. Similarly, when it has a phosphate, it becomes dependent on sodium.

This latter finding was key to learning just how ATPase moved sodium out of the cell. ATPase molecules are set into the cell membrane, and they consist of two parts, one that stabilizes the enzyme and the other that carries out activity.

Part of the enzyme pokes inside the cell. There, one ATP molecule and three sodium ions can bind to it at a time. A phosphorus group is taken from the ATP to bind to the enzyme, and the remaining ADP is released. The enzyme then changes shape, carrying the attached sodium ions with it to the outside of the cell membrane. There, they are released into the cell's surroundings, as is the attached phosphorus. In place of the three sodium ions, two potassium ions attach themselves to the enzyme, which again changes shape and carries the K+ into the cell's interior.

This activity uses up about one-third of the ATP that the body produces each day, which can range from about half of a resting person's body weight to almost one ton in a person who is doing strenuous activity.

Thanks to this molecular pump, the cell is able to maintain its balance of potassium ions on the inside and sodium ions on the outside, regulating the electrical charges that allow cells to pass along or react to stimulation from nerve cells.

This enzyme is important for other reasons as well. For example, the pump's action on the balance of sodium and potassium makes it possible for the cell to take in nutrients and to expel waste products. If the molecular pump were to stop--as it can when a lack of nourishment or oxygen shuts down ATP formation--the cell would swell up, and it would be unable to pass along nerve impulse. If this were to happen in the brain, unconsciousness would rapidly follow.

Since Skou discovered ATPase, scientists have found other molecular pumps hard at work in the cell. They include H+, K+-ATPase, which produces stomach acid, and Ca2+-ATPase, which helps control the contraction of muscle cells.

Retired in 1988, Skou and his wife Ellen have two daughters and several grandchildren. He keeps an office at the University of Aarhus Department of Biophysics.