THE MAJOR STRUCTURE OF THE RIBOSOME, the cell's factory for assembling proteins, has been solved by crystallographers, boosting hopes for powerful new drugs that disarm an invader's ability to make proteins. In addition, the new result suggests that the ribosome's RNA is responsible for assembling amino acids into proteins. At last month's meeting of the American Crystallographic Association, Yale researchers (groups led by Thomas Steitz, 203-432-5619, and Peter Moore, 203-432-3995) presented the most comprehensive atom-scale maps yet of the larger of two subunits in a bacterial ribosome. Probed with x rays at Brookhaven and Argonne synchrotrons, the subunit (which looks like a somewhat flattened lower half of a snowman) is the largest asymmetric molecular structure (50 times larger than the average enzyme) that's yet been mapped at the atomic scale (2.4 angstrom resolution).

The researchers found that the ribosome contains RNA at its very core, with surrounding proteins stabilizing it. They identified an adenosine base in RNA as the site that catalyzes the formation of "peptide bonds" which string together amino acids to form proteins. Additional biochemical work (Scott Strobel, 203-432-9772) on a different bacterium confirms the RNA region as one of high acidity, indicating fervent chemical activity. Together, this evidence supports the idea that RNA performed the first biochemical reactions important for life. (See Ban et al., Nissan et al., Muth et al., Science, 11 August 2000.)