Ribosome at work

For the first time, scientists were able to examine a separate ribosome at work. An international group of biochemists from the USA, Brazil and Japan, led by Ignacio Tinoco from the University of California, took a single strand of matrix RNA, self-organized into a hairpin structure. The free 3’ and 5’ ends of the MRNA were attached to tiny polymer beads. One of the beads was fixed in a static position, the other was carefully held using optical tweezers – two highly focused laser beams. Any movement of the optical tweezers by magnitudes of the order of nanometers could be accurately measured.

A single ribosome was attached to the mr-RNA below in the direction of movement from the hairpin. As the ribosome moves through the MRNA, the hairpin opens, allowing the reading of the genetic code. During this process, the RNA resembled an opening lightning bolt. The "lightning movement" can be measured using optical tweezers; thus, it becomes possible to directly monitor the movement of the ribosome.

The study showed that the process taking place on the ribosome includes two stages. First of all, the ribosome reads three letters of the RNA codon code, each of which corresponds to one amino acid transferred to the ribosome by means of transport RNA, and attached to the growing peptide chain. This part of the process usually takes place within a few seconds until the ribosome is "convinced" that the right amino acid is embedded in the right place.

After this process is completed, the ribosome is stretched to contact with the next codon – this process takes no more than a tenth of a second.

Article by Jin-Der Wen et al. Following translation by single ribosomes one codon at a time published in the electronic version of Nature 09.03.2008

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12.03.2008