Yale Bulletin and Calendar

February 18, 2000

Volume 28, Number 21

Research on extremophiles
may lead to better antibiotics

Yale scientists have discovered that a single enzyme found in certain organisms is capable of providing two amino acids in protein synthesis, increasing the possibility of creating improved antibiotics.

This discovery solves the last remaining mystery surrounding the sequence of genomes in some extremophiles -- organisms that live under extreme temperature and severe environmental conditions -- says Dieter Söll, professor of molecular biophysics and biochemistry, and of molecular cell and developmental biology.

Past research on extremophiles produced numerous surprises for the world of molecular biology. The most important, notes Söll, was the discovery that some of these organisms lack enzymes that are essential for reading the genetic code -- the blueprint of life -- leaving scientists with the question: "How are all the amino acids that are found in proteins encoded during protein synthesis?"

The answer, says Söll, is by borrowing proteins previously thought to be solely responsible for recognizing single amino acids in this same process. The results of the study were published in a recent issue of Science.

"Beyond its immediate impact on the field of anti-infective drug development, this result also calls into question part of the famous 'adaptor hypothesis' developed by Francis Crick, which has been a principle for protein synthesis for over four decades," says Söll.

Aminoacyl-tRNA synthetases are a family of cellular components crucial for translating the genetic message into proteins; they activate a single amino acid in this process. Because certain genomes lack a recognizable gene for cysteinyl-tRNA synthetase, the enzyme responsible for cysteine insertion, the Söll lab instead isolated a protein with the corresponding activity. When they analyzed this protein, it turned out to be the enzyme that usually carries out this function for the amino acid proline.

"Surprisingly, unlike the current concept, this enzyme carries out the insertion of two amino acids in an accurate fashion," says Söll.

While the primary interest of the Söll group has been to address a fundamental question in molecular biology, this result has broader implications. The aminoacyl-tRNA synthetases have come under increasing scrutiny in recent years as potential new targets for the development of much-needed anti-infective drugs. The discovery that some of these enzymes may harbor unexpected secondary activities may explain why some of these targets have not yet realized their full potential.

Söll's research team in the Department of Molecular Biophysics and Biochemistry included Constantinos Stephonopoulos, Tony Li, Randy Longman, Uta C. Vothknecht and Hubert D. Becker. The team also included Michael Ibba of the Department of Medical Biochemistry, Coppenhagen, North Denmark.

-- By Karen Peart

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