Nobel Laureate: Tom Cech

 

The Nobel Prize in Chemistry 1989.

"for their discovery of catalytic properties of RNA"



In 1989, Thomas R. Cech (1947 - ) was awarded the Nobel Prize in Chemistry for discovering that the ribosomal RNA precursor from Tetrahymena catalyzed its own self-splicing reaction. [Ribosomal RNA Genes in Eukaryotes]. He shared the prize with Sydney Altman who worked RNase P.

The presentation speech was delivered by Professor Bertil Andersson of the Royal Swedish Academy of Sciences.
THEME:

Nobel Laureates

Your Majesties, Your Royal Highnesses, Ladies and Gentlemen,

The cells making up such living organisms as bacteria, plants, animals and human beings can be looked upon as chemical miracles. Simultaneously occurring in each and every one of these units of life, invisible to the naked eye, are thousands of different chemical reactions, necessary to the maintenance of biological processes. Among the large number of components responsible for cell functions, two groups of molecules are outstandingly important. They are the nucleic acids - carriers of genetic information - and the proteins, which catalyze the metabolism of cells through their ability to act as enzymes.

Genetic information is programmed like a chemical code in deoxyribonucleic acid, better known by its abbreviated name of DNA. The cell, however, cannot decipher the genetic code of the DNA molecule directly. Only when the code has been transferred, with the aid of enzymes, to another type of nucleic acid, ribonucleic acid or RNA, can it be interpreted by the cell and used as a template for producing protein. Genetic information, in other words, flows from the genetic code of DNA to RNA and finally to the proteins, which in turn build up cells and organisms having various functions. This is the molecular reason for a frog looking different from a chaffinch and a hare being able to run faster than a hedgehog.


Life would be impossible without enzymes, the task of which is to catalyze the diversity of chemical reactions which take place in biological cells. What is a catalyst and what makes catalysis such a pivotal concept in chemistry? The actual concept is not new. It was minted as early as 1835 by the famous Swedish scientist Jöns Jacob Berzelius, who described a catalyst as a molecule capable of putting life into dormant chemical reactions. Berzelius had observed that chemical processes, in addition to the reagents, often needed an auxiliary substance - a catalyst - to occur. Let us consider ordinary water, which consists of oxygen and hydrogen. These two substances do not react very easily with one another. Instead, small quantities of the metal platinum are needed to accelerate or catalyze the formation of water. Today, perhaps, the term catalyst is most often heard in connection with purification of vehicle exhausts, a process in which the metals platinum and rhodium catalyze the degradation of the contaminant nitrous oxides.

As I said earlier, living cells also require catalysis. A certain enzyme, for example, is needed to catalyze the breakdown of starch into glucose and then other enzymes are needed to burn the glucose and supply the cell with necessary energy. In green plants, enzymes are needed which can convert atmospheric carbon dioxide into complicated carbon compounds such as starch and cellulose.

As recently as the early 1980s, the generally accepted view among scientists was that enzymes were proteins. The idea of proteins having a monopole of biocatalytic capacity has been deeply rooted, and created a fundamental dogma of biochemistry. This is the very basic perspective in which we have to regard the discovery today being rewarded with the Nobel Prize for Chemistry. When Sidney Altman showed that the enzyme denoted RNaseP only needed RNA in order to function, and when Thomas Cech discovered self-catalytic splicing of a nucleic acid fragment from an immature RNA molecule, this dogma was well and truly holed below the waterline. They had shown that RNA can have catalytic capacity and can function as an enzyme. The discovery of catalytic RNA came as a great surprise and was indeed met with a certain amount of scepticism. Who could ever have suspected that scientists, as recently as in our own decade, were missing such a fundamental component in their understanding of the molecular prerequisites of life? Altman's and Cech's discoveries not only mean that the introductory chapters of our chemistry and biology textbooks will have to be rewritten, they also herald a new way of thinking and are a call to new biochemical research.

The discovery of catalytic properties in RNA also gives us a new insight into the way in which biological processes once began on this earth, billions of years ago. Researchers have wondered which were the first biological molecules. How could life begin if the DNA molecules of the genetic code can only be reproduced and deciphered with the aid of protein enzymes, and proteins can only be produced by means of genetic information from DNA? Which came first, the chicken or the egg? Altman and Cech have now found the missing link. Probably it was the RNA molecule that came first. This molecule has the properties needed by an original biomolecule, because it is capable of being both genetic code and enzyme at one and the same time.

Professor Altman, Professor Cech, you have made the unexpected discovery that RNA is not only a molecule of heredity in living cells, but also can serve as a biocatalyst. This finding, which went against the most basic dogma in biochemistry, was initially met with scepticism by the scientific community. However, your personal determination and experimental skills have overcome all resistance, and today your discovery of catalytic RNA opens up new and exciting possibilities for future basic and applied chemical research.

In recognition of your important contributions to chemistry, the Royal Swedish Academy of Sciences has decided to confer upon you this year's Nobel Prize for Chemistry. It is a privilege and pleasure for me to convey to you the warmest congratulations of the Academy and to ask you to receive your prizes from the hands of His Majesty the King.

---

[Image Credit: Structure of the self-slicing ribosomal RNA precursor from Tom Cech Lab]