The Nobel Prize in Chemistry 1997

Jens C. Skou

Jens C. Skou was one of three men who shared the 1997 Nobel Prize in Chemistry. Skou received the award in recognition of discovering the first "molecular pump," Na+, K+ ATPase, an enzyme that promotes movement through the membrane surrounding a cell and maintains the balance of sodium ions (Na+) and potassium ions (K+) in a living cell.

Jens Christian Skou was born October 8, 1918, in Lemvig, Denmark, to Magnus Martinus Skou, a timber merchant, and Ane-Margrethe (Jensen Knak) Skou. 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. In 1948 he married Ellen-Margrethe (Nielsen); they have two children, Hanne and Karen.

After receiving his M.D., Skou went for clinical training at the Hospital at Hj?rring 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 the same year he received his Doctor of Medical Sciences degree, he became associate professor at the institute. In 1963 Skou became a full professor and was named chairman of the Institute of Physiology. From 1978-1988, he was professor of biophysics at the University of Aarhus.

Skou has devoted his career to both education and research. He has served as an advisor for many Ph.D. and doctor of medical science students and as an examiner at doctoral dissertation presentations. He has published more than 90 papers on his research, which has investigated the actions of local anesthetics and what mechanisms made them work, as well as the work that earned him the 1997 Nobel Prize, 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 that of the cell's 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). ATP was discovered in 1929 by German chemist Karl Lohmann. Further research by Franz Lippman between 1939 and 1941 showed that ATP carries chemical energy in the cell. It has been called the cell's "energy currency." 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 finely found 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--called 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. Years of further experimentation followed. In them, Skou 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 discovered that this freed phosphate bound to the ATPase as well, a process known as phosphorylation. The presence or absences of this phosphate changed the enzyme's interaction with sodium and potassium ions, Skou discovered. When the ATPase lacked a phosphate group, it became dependent on potassium. Similarly, when it has a phosphate, it became dependent on sodium.

This latter discovery 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 which stabilizes the enzyme and the other which 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, maintaining the electrical charges that allow cells to pass along or to react to stimulation from nerve cells.

This enzyme is important for other reason 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.

In addition to the Nobel Prize, Skou has received much recognition for his work. He is a regular participant and organizer of symposia on transmembrane transport. In addition, he has received the Leo Prize, the Novo Prize, the Swedish Medical Association's Anders Retzius gold medal, and the Dr. Eric K. Ferntroms Big Nordic Prize.

He is a member of the Danish Royal Academy, and has served on a number of its committees and science foundation board. He is also a member of the Danish Royal Society, the Deutsche Akademie der Naturfoscher, Leopoldins, and the European Molecular Biology Organization (EMBO). He is a foreign associate of the American National Academy of Sciences. In addition, Skou is an honorary member of the Japanese Biochemical Society and the American Physiological Society. He received and honorary doctorate from the University of Copenhagen. Skou lives in Denmark.

I was born on the 8th of October 1918 into a wealthy family in Lemvig, a town in the western part of Denmark. The town is nicely situated on a fjord, which runs across the country from the Kattegat in East to the North Sea in West. It is surrounded by hills, and is only 10 km, i.e. bicycling distance, from the North Sea, with its beautiful beaches and dunes. My father Magnus Martinus Skou together with his brother Peter Skou were timber and coal merchants.

We lived in a big beautiful house, had a nice summer house on the North Sea coast. We were four children, I was the oldest with a one year younger brother, a sister 4 years younger and another brother 7 years younger. The timber-yard was an excellent playground, so the elder of my brothers and I never missed friends to play with. School was a minor part of life.

When I was 12 years old my father died from pneumonia. His brother continued the business with my mother Ane-Margrethe Skou as passive partner, and gave her such conditions that there was no change in our economical situation. My mother, who was a tall handsome woman, never married again. She took care of us four children and besides this she was very active in the social life in town.

When I was 15, I went to a boarding school, a gymnasium (high school) in Haslev a small town on Zealand, for the last three years in school (student exam). There was no gymnasium in Lemvig.

Besides the 50-60 boys from the boarding section of the school there were about 400 day pupils. The school was situated in a big park, with two football fields, facilities for athletics, tennis courts and a hall for gymnastics and handball. There was a scout troop connected to the boarding section of the school. I had to spend a little more time preparing for school than I was used to. My favourites were the science subjects, especially mathematics. But there was plenty of time for sports activities and scouting, which I enjoyed. All the holidays, Christmas, Easter, summer and autumn I spent at home with my family.

After three years I got my exam, it was in 1937. I returned to Lemvig for the summer vacation, considering what to do next. I could not make up my mind, which worried my mother. I played tennis with a young man who studied medicine, and he convinced me that this would be a good choice. So, to my mother's great relief, I told her at the end of August that I would study medicine, and started two days later at the University of Copenhagen.

The medical course was planned to take 7 years, 3 years for physics, chemistry, anatomy, biochemistry and physiology, and 4 years for the clinical subjects, and for pathology, forensic medicine, pharmacology and public health. I followed the plan and got my medical degree in the summer of 1944.

I was not especially interested in living in a big town. On the other hand it was a good experience for a limited number of years to live in, and get acquainted with the capital of the country, and to exploit its cultural offers. Art galleries, classical music and opera were my favourites.

For the first three years I spent the month between the semesters at home studying the different subjects. For the last 4 years the months between the semesters were used for practical courses in different hospital wards in Copenhagen.

It was with increasing anxiety that we witnessed to how the maniac dictator in Germany, just south of our border, changed Germany into a madhouse. Our anxiety did not become less after the outbreak of the war. In 1914 Denmark managed to stay out of the war, but this time, in April 1940 the Germans occupied the country. Many were ashamed that the Danish army were ordered by the government to surrender after only a short resistance. Considering what later happened in Holland, Belgium and France, it was clear that the Danish army had no possibility of stopping the German army.

The occupation naturally had a deep impact on life in Denmark in the following years, both from a material point of view, but also, what was much worse, we lost our freedom of speech. For the first years the situation was very peculiar. The Germans did not remove the Danish government, and the Danish government did not resign, but tried as far as it was possible to minimize the consequences of the occupation. The army was not disarmed, nor was the fleet. The Germans wanted to use Denmark as a food supplier, and therefore wanted as few problems as possible.

The majority of the population turned against the Germans, but with no access to weapons, and with a flat homogeneous country with no mountains or big woods to hide in, the possibility of active resistance was poor. So for the first years the resistance only manifested itself in a negative attitude to the Germans in the country, in complicating matters dealing with the Germans as far as possible, and in a number of illegal journals, keeping people informed about the situation, giving the information which was suppressed by the German censorship. There was no interference with the teaching of medicine.

The Germans armed the North Sea coast against an invasion from the allied forces. Access was forbidden and our summer house was occupied. My grandmother had died in 1939, and we four children inherited what would have been my father's share. For some of the money my brother and I bought a yacht, and took up sailing, and this has since been an important part of my leisure time life. After the occupation the Germans had forbidden sailing in the Danish seas except on the fjord where Lemvig was situated, and another fjord in Zealand.

The resistance against the Germans increased as time went on, and sabotage slowly started. Weapons and ammunition for the resistance movement began to be dropped by English planes, and in August 1943 there were general strikes all over the country against the Germans with the demand that the Government stopped giving way to the Germans. The Government consequently resigned, the Germans took over, the Danish marine sank the fleet and the army was disarmed. An illegal Frihedsr?d (the Danish Liberation Council) revealed itself, which from then on was what people listened to and took advice from.

Following this, the sabotage against railways and factories working for the Germans increased, and with this arrests and executions. One of our medical classmates was a German informer. We knew who he was, so we could take care. He was eventually liquidated by unknowns. We feared a reaction from Gestapo against the class, and stayed away from the teaching.

The Germans planned to arrest the Jews, but the date, the night between the first and second October 1943 was revealed by a high placed German. By help from many, many people the Jews were hidden. Of about 7000, the Germans caught 472, who were sent to Theresienstadt where 52 died. In the following weeks illegal routes were established across the sea, ?resund, to Sweden, and the Jews were during the nights brought to safety. From all sides of the Danish society there were strong protests against the Germans for this encroachment on fellow-countrymen.

In May and June 1944, we managed to get our exams. A number of our teachers had gone underground, but their job was taken over by others. We could not assemble to sign the Hippocratic oath, but had to come one by one at a place away from the University not known by others.

I returned to my home for the summer vacation. The Germans had taken over part of my mother's house, and had used it for housing Danes working for the Germans. This was extremely unpleasant for my mother, but she would not leave her house and stayed. I addressed the local German commander, and managed to get him to move the "foreigners" from the house at least as long as we four children were home on holiday.

The Germans had forbidden sailing, but not rowing, so we bought a canoe and spent the holidays rowing on the fjord.

After the summer holidays I started my internship in a hospital in Hj?rring in the northern part of the country. I first spent 6 months in the medical ward, and then 6 months in the surgical ward. I became very interested in surgery, not least because the assistant physician, next in charge after the senior surgeon, was very eager to teach me how to make smaller operations, like removing a diseased appendix. I soon discovered why. When we were on call together and we during the night got a patient with appendicitis, it happened--after we had started the operation--that he asked me to take over and left. He was then on his way to receive weapons and explosives which were dropped by English planes on a dropping field outside Hj?rring. I found that this was more important than operating patients for appendicitis, but we had of course to take care of the patients in spite of a war going on. He was finally caught by the Gestapo, and sent to a concentration camp, fortunately not in Germany, but in the southern part of Denmark, where he survived and was released on the 5th of May 1945, when the Germans in Denmark surrendered.

I continued for another year in the surgical ward. It was here I became interested in the effect of local anaesthetics, and decided to use this as a subject for a thesis. Thereafter I got a position at the Orthopaedic Hospital in Aarhus as part of the education in surgery.

In 1947 I stopped clinical training, and got a position at the Institute for Medical Physiology at Aarhus University in order to write the planned doctoral thesis on the anaesthetic and toxic mechanism of action of local anaesthetics.

During my time in Hj?rring I met a very beautiful probationer, Ellen Margrethe Nielsen, with whom I fell in love. I had become ill while I was on the medical ward, and spent some time in bed in the ward. I had a single room and a radio, so I invited her to come in the evening to listen to the English radio, which was strictly forbidden by the Germans - but was what everybody did.

After she had finished her education as a nurse in 1948, she came to Aarhus and we married. In 1950 we had a daughter, but unfortunately she had an inborn disease and died after 1 1/2 years. Even though this was very hard, it brought my wife and I closer together. In 1952, and in 1954 respectively we got two healthy daughters, Hanne and Karen.

The salary at the University was very low, so partly because of this but also because I was interested in using my education as a medical doctor, I took in 1949 an extra job as doctor on call one night a week. It furthermore had the advantage that I could get a permission to buy a car and to get a telephone. There were still after war restrictions on these items.

I was born in a milieu which politically was conservative. The job as a doctor on call changed my political attitude and I became a social democrat. I realized how important it is to have free medical care, free education with equal opportunities, and a welfare system which takes care of the weak, the handicapped, the old, and the unemployed, even if this means high taxes. Or as phrased by one of our philosophers, N.F.S. Grundtvig, "a society where few have too much, and fewer too little".

We lived in a flat, so the car gave us new possibilities. We wanted to have a house, and my mother would give us the payment, but I was stubborn, and wanted to earn the money myself. In 1957 we bought a house with a nice garden in Risskov, a suburb to Aarhus not far away from the University.

I am a family man, I restricted my work at the Institute to 8 hours a day, from 8 to 4 or 9 to 5, worked concentratedly while I was there, went home and spent the rest of the day and the evening with my wife and children. All weekends and holidays, and 4 weeks summer holidays were spent with the family. In 1960 we bought an acre of land on a cliff facing the beach 45 minutes by car from Aarhus, and built a small summer house. From then on this became the centre for our leisure time life. We bought a dinghy and a rowing boat with outboard motor and I started to teach

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