Sidney Altman

(b. 1939)

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(1939– American chemist

Born in Montreal, Canada, Altman was educated at the University of Colorado, Boulder, where he obtained his PhD in 1967. He moved to Yale in 1971, becoming professor of biology in 1980 and a naturalized US citizen in 1984.

In 1982 Thomas Cech at Colorado had shown that RNA sometimes served as a biocatalyst – a role previously thought to be exclusive to protein enzymes. Cech's work was on a reaction in which the RNA was a self-catalyst. Altman set out to investigate other catalytic activity of RNA.

He worked with ribonuclease-P, an enzyme composed of both RNA and a protein, which catalyzes the processing of transfer RNA (tRNA). For the enzyme to work at the cellular level, it was thought that both protein and RNA were needed. It could, however, be possible that the RNA was merely a kind of structural support for the protein enzyme. Altman found that, in vitro, ribonuclease-P alone could splice the tRNA molecule at the correct place; the unaccompanied protein displayed no such activity.

Final proof came when a recombinant DNA template was used to produce only the RNA part of the ribonuclease-P. The artificial RNA still catalyzed the appropriate activity without any associated protein whatsoever. Altman had thus helped to break down the previously unquestioned dogma that molecules could either carry information, like RNA, or catalyze chemical reactions, like proteins, but they could not do both. The discovery could also throw light on the puzzle that if proteins are needed to assemble RNA, and RNA to assemble proteins, then how did the process ever get started? The answer could lie in the catalytic activity of RNA itself.

For his work on ribonuclease-P Altman shared the 1989 Nobel Prize for chemistry with Thomas Cech.

Subjects: Science and Mathematics.

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