Using x-ray crystallography, two research teams from the Howard Hughes Medical Institute (HHMI), working independently, have found that catalytic RNA, like its protein cousins, is ready to function as soon as it is produced.

Ever since HHMI investigator Thomas Cech at the University of Colorado in Boulder uncovered the catalytic properties of RNA in 1982, researchers have been diligently studying these ribozymes. Scientists have since discovered more than 500 ribozymes in a diverse range of organisms and have found that they share many similarities with their more widespread protein cousins, enzymes.

"The finding of an enzyme-like active site fits right in with the story we've been building about ribozymes. But a picture is worth a thousand words and now we've got the picture," says Cech, who won the 1989 Nobel Prize in Chemistry for his discovery of ribozymes.

The results of Cech's group, spearheaded by HHMI associate Barbara Golden, appear in the October 9, 1998, issue of Science. They describe the three-dimensional structure of the largest ribozyme ever crystallized, which comes from the organism Tetrahymena thermophila. In the October 8, 1998, issue of Nature, HHMI investigator Jennifer Doudna and colleagues from Yale University detail the structure of a smaller ribozyme from the human pathogen, hepatitis delta virus (HDV).

Crystallizing RNAs is notoriously tricky. Crystals contain billions of molecules that must be aligned precisely if they are to provide a sharp image of a molecule's three-dimensional structure. But RNA molecules are difficult to align because they don't usually have many surface "nooks and crannies" to help the molecules stick together within the crystal. While Doudna's group could easily crystallize the viral ribozyme, most of the crystals they created didn't interact well with x rays. Inspired by "desperation," Doudna
'"/>

Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
9-Oct-1998