The crucial job of reading the genetic instructions and synthesizing the specified proteins is carried out by ribosomes, tiny protein factories humming away inside the cells of all living things. The researchers used a technique called x-ray crystallography, which involves growing crystals of purified >ribosomes, shining a focused beam of x-rays through the crystals, and analyzing the resulting diffraction pattern.
Noller's laboratory achieved breakthroughs in 1999 and 2001, producing the first high-resolution images of the molecular structure of a complete ribosome. Now, his team has made another major advance with an even higher-resolution image that enables them to construct an atom-by-atom model of the ribosome.
The new picture shows details never seen before and suggests how certain parts of the ribosome move during protein synthesis. The bacterial ribosomes studied in Noller's lab (obtained from the bacterium Thermus thermophilus) are made up of three different RNA molecules and more than 50 different proteins.
The results provide a snapshot of the molecular machine in action. By comparing his images with those obtained by other groups that have caught the ribosome or its subunits in different positions, Noller is finding clues to the molecular motions with which the ribosome does its work.
"Our next goal is to trap the ribosome in other functional states to get more frames of the movie," he said.