Sidney Altman: Complete Life and Legacy of the Scientist Who Found Catalytic RNA

Sidney Altman (1939–2022) was a Canadian-American molecular biologist who spent most of his career at Yale University. His discovery that the RNA component of ribonuclease P can act as a catalyst overturned the long-held belief that all enzymes are proteins. For this he shared the 1989 Nobel Prize in Chemistry with Thomas Cech. His legacy: he opened a new chapter in biochemistry in which RNA is both a carrier of information and a molecular machine.

Early Life and Family

Sidney Altman was born on 7 May 1939 in Montreal, Quebec, Canada. His parents were immigrants: his father worked in a grocery business and his mother worked in a textile factory, and the family lived in a modest neighbourhood. He was the younger of two sons. He has described a childhood in which education was valued highly, and he credited his parents with encouraging his interest in learning. The family circumstances were simple, but the hard work of his parents set an example that stayed with him throughout his life.

Education and Mentors

Altman studied physics at the Massachusetts Institute of Technology (MIT), graduating in 1960. Afterwards he moved toward biology and biophysics. He began graduate study in physics at Columbia University, then moved to the University of Colorado Medical Center in Denver, where he completed his PhD in biophysics in 1967 under Leonard Lerman. His thesis dealt with the interaction of acridine dyes with DNA. He then did postdoctoral work at Harvard University with Mathew Meselson, and later at the MRC Laboratory of Molecular Biology in Cambridge, England, where he worked with Sydney Brenner and Francis Crick. There he began work on tRNA, which he continued for the rest of his career.

Career Timeline

Major Scientific Contributions

The principal contribution is the demonstration of catalytic RNA in ribonuclease P. RNase P removes the 5′ leader sequence from precursor tRNA. Using purified components from E. coli, Altman, Cecilia Guerrier-Takada and colleagues showed that the RNA subunit alone (M1 RNA) cleaves its substrate at high magnesium ion concentration, while the protein subunit alone does not. This showed that RNA is the catalyst and the protein is a helper.

Other contributions include:

• Structure and mechanism of RNase P: work on folding, substrate recognition and the role of metal ions.
• Human RNase P: studies of the human enzyme, in which RNA and several protein subunits operate together.
• External guide sequences: a strategy in which short RNA molecules direct RNase P to cut a chosen target RNA, explored as a possible way to block gene expression, for example in bacteria and viruses.

Awards, Honours and Nobel Prize

The Nobel Prize in Chemistry 1989 was awarded jointly to Sidney Altman and Thomas R. Cech "for their discovery of catalytic properties of RNA." It was a Chemistry prize, though the subject is often taught in biology as well. Altman held the title of Sterling Professor at Yale and served as Dean of Yale College before and during the time of the award. He was a member of national academies in the United States and received various other honours.

Personality, Struggles and Lesser-Known Facts

• A physicist who became a biologist: Altman's undergraduate degree was in physics, and he moved to biology after being interested in how genes work. This mix helped him to ask quantitative questions.
• Years of doubt: When the first results appeared, many scientists suspected contamination with a protein. Controls and repeated experiments, including destroying the RNA with ribonuclease, were needed to convince the field.
• A shared discovery: His result and Cech's finding about self-splicing introns came at about the same time from different systems, and together they made a convincing case.
• Dean and scientist: He combined research with administrative responsibility as Dean of Yale College, and he cared about undergraduate education.
• Immigrant story: The son of immigrants who worked in a grocery business and a factory, he rose to the highest level in science.

Legacy and Influence on Modern Chemistry

The discovery of ribozymes changed the way scientists look at the origin of life. If RNA can carry information and also catalyse reactions, then a world dominated by RNA could have preceded the modern world of DNA and proteins. The ribosome, shown later to be a ribozyme in which RNA forms the peptide bond, strengthened this view. Today, researchers design artificial ribozymes, study riboswitches and develop RNA-based drugs. In India, students meet these ideas in biochemistry and molecular biology courses, and the topic is a favourite in CSIR-NET life sciences and chemical sciences papers.

Lessons for Students

1. Test assumptions. Even a rule found in all textbooks may have exceptions.
2. Use strong controls. The claim was accepted because the controls excluded protein contamination.
3. Collaborate across disciplines. Physics, chemistry and biology all contributed.
4. Stay with a problem. Altman worked on tRNA processing for years before the key result.

FAQ

Where did Altman work most of his life?

At Yale University in New Haven, Connecticut, from 1971.

What is RNase P?

An enzyme made of RNA and protein that processes the 5′ end of precursor tRNA.

Who shared the 1989 Nobel Prize with Altman?

Thomas Cech, for the discovery of catalytic properties of RNA.

Why is the discovery important?

It showed that RNA can be a catalyst, supporting ideas about the origin of life and opening new fields in RNA biology.

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