The ribosome: the key to life at the atomic level part XNUMX - Ada Yonat - the persistent pioneer

The continuation of the popular review (part three of four) and in it the background to the decision of the Nobel Prize Committee in Chemistry to award the prize to the discoverers of ribosomes, including Prof. Ada Yonat from the Weizmann Institute

Sometimes, a breakthrough discovery comes from a pioneering scientist who explores a new and unfamiliar field. In this case, the pioneer was Ada Yonet. In the late seventies she decided to try and obtain X-ray crystallographic structures of the ribosome. However, at that point in time, most scientists considered the task impossible.

In X-ray crystallography (Wikipedia entry) scientists aim a beam of X-rays at a crystal, for example, a protein. When the rays hit the atoms of the crystal they are scattered out of it. On the other side of the crystal, the scientists record the way the rays scatter. In the past, this was done by using photographic film, which was blackened as a result of being hit by the rays. Today, scientists use CCD type detectors found in digital cameras (and which are the focus of the 2009 Nobel Prize in Physics). By analyzing the resulting dot patterns, scientists are able to accurately determine the spatial location of the atoms that make up the crystalline protein.

In order for this measurement to succeed, the crystal must be almost perfect; The separate is required to create a precise pattern that repeats itself cyclically. With a little luck, when the salt water is allowed to slowly evaporate, spectacular salt crystals form. However, if the pot full of this brine is allowed to heat to dryness, the salt will only form an irregular layer at the bottom. That is - different conditions will lead to different results in the formation efficiency of materials. To a large extent, the same is true for X-ray crystallography. Obtaining high quality crystals from a protein can be an extremely challenging task and the more complex the protein, the more difficult the task.

Because of this, many of the scientists working in the field were extremely skeptical about Ada Yonat's vision. The ribosome is one of the protein/RNA conjugates. the most complex in existence. It is separated into two parts, the "small subunit" and the "large subunit". The small subunit in the human ribosome consists of an RNA fragment. long and about thirty-two proteins. The large subunit consists of three RNA fragments. and about forty-six proteins. Therefore, each of the subunits contains thousands of nucleotides and thousands of amino acids, where each of these components in turn consists of thousands of different atoms. Ada Yonat wanted to determine the exact location of each and every one of these atoms in the ribosome.

Hot springs and the Dead Sea - a dare came out sweet

When Ada Yonat decided to synthesize the ribosome, she chose to work with bacteria living in harsh and harsh conditions. The bacterium, Geobacillus stearothermophilus, is able to live in hot springs and survive in temperatures of up to seventy-five degrees Celsius. Ada Yonath's hypothesis was that in order to do this, the bacterium's ribosome must be extremely stable and therefore could lead to the creation of better quality crystals.

In 1980 she was already able to create the first three-dimensional crystals of the large subunit of the ribosome. It was a considerable achievement, even though the crystals were far from perfect.

In fact, it will take another twenty years of hard work before Ada Yonat will be able to obtain a picture of the ribosome in which she will be able to determine the exact position of each of the atoms. She tried many new measures along the way. For example, she stabilized the crystals by freezing them in liquid nitrogen at a temperature of minus 196 degrees Celsius. She tried to synthesize ribosomes from other tough microorganisms. One of them is found nearby - the salt-loving bacterium Haloarcula marismortui living in the Dead Sea.

Step by step, with determination, Ada Yonat approached her goal. Eventually, the scientists realized that it was indeed possible to map the atomic structure of the ribosome and more and more researchers joined the race. Among them were the other two researchers, who share the Nobel Prize with Ada Yunath, Venkataraman Ramakrishnan and Thomas Straits.

For the source of the review on the Nobel Prize website

To the first part of the review - from Darwin to Watson and Crick

To the second part - what is the ribosome

More of the topic in Hayadan:

• The work of Prof. Yonat made it possible to understand the mode of action of five antibiotic drugs
• Ada Yonat won the 2009 Nobel Prize in Chemistry
• For an interview with Ada Yonat that was published in Scientific American about a year ago - polar bears and drunken ribosomes
• The ribosome cracker - an interview for the Weizmann Institute magazine
• The mysteries of the peptide bond - Weizmann Institute magazine