This post was contributed by Kevin Beier
DNA is a crucial element of life, acting as the blueprint for the existence of all living organisms. However, DNA alone is not sufficient for life. There must be translators of the DNA to make proteins and other components that allow cells to function. One such essential component is the ribosome. This year’s chemistry Nobel Prize went to Venkatraman Ramakrishnan, Thomas A. Steitz and Ada E. Yonath, who showed how the ribosome functions. The ribosome is a small component of a cell that “translates” genetic material into the components that are necessary for life. Each organism, including bacteria, plants, and animals, has DNA, which acts as the blueprint for the organism. This DNA has all of the information needed to make life: contained within it is what makes humans different from mice, and what makes some humans different from other humans. However, just as a blueprint contains only the directions to construct a house and not the laborers that make the construction happen, DNA contains the information to make an organism, but cannot do so alone. Just as construction workers are required to build the house, the cell needs its own “workers” to construct the cell. One of these workers in the cell is the ribosome, which acts to change the language of DNA into functional units – proteins – which perform many of the critical functions within our cells.
The existence of the ribosome has been known for decades, and its importance has been appreciated for many years. However, as a very complex machine, scientists did not have a good understanding of how this machine worked. Only through knowledge of how this complicated machinery works can we alter it in ways beneficial for people, for example curing diseases – such as macrocytic anemia and leukemia – that are caused by malfunctioning ribosomes. The Nobel Prize-winning work by Ramakrishnan, Steitz, and Yonath focused on the understanding of this machine. Using a technique known as X-ray crystallography, these researchers were able to build a very accurate map of this machine, which allowed us to understand how the parts of the machine interact with one another. The ribosome itself is made up of multiple parts, which act together to make a working ribosome. This is similar to the way that a computer is composed of parts such as a keyboard, a screen, a mouse, a printer, and many more – parts that don’t function independently but together can form a functional unit. The ribosome is itself composed of numerous small proteins and nucleic acids similar to DNA, known as rRNA. The ribosome also uses molecules called tRNAs, which act as the actual translators of the ribosome, converting the nucleic acid language into that of proteins. tRNAs and rRNAs are similar to mRNAs – the intermediate between DNA and protein – but perform different functions in the cell. While each of the components of the ribosome was known, an understanding of the fine resolution in which they interacted remained unknown.
Using X-ray crystallography, much like modern X-rays taken at the hospital, the scientists were able to construct images of the ribosome. X-rays are shined on the ribosomes, and the rays are collected by a computer, which can use the pattern of rays to construct the image. Similar to the way in which light reflects off of a mirror, X-rays will “diffract” from atoms: the atom changes the path the X-ray takes. The ways in which this diffraction occurs are predictable, and thus the diffraction patterns can be used to form an image, allowing scientists to infer the shape of the molecule being studied.
Perhaps the most important immediate impact of this work was that, with such an accurate map of the ribosome, scientists are now able to design drugs that affect the ribosome in particular ways. For example, the ribosomes of bacteria perform the same function as those of animals – they make proteins from the information provided by the DNA. However, they are different, much as while computers come in many different models, they all have similar functions (ability to perform calculations, access the internet, etc). Scientists can make drugs that prevent bacterial ribosomes from producing bacterial proteins while not affecting human ribosomes, thereby curing many diseases caused by bacterial infections. In addition to being a major advancement in our understanding of biology, this work received the Nobel Prize because it has helped in the development of novel and useful antibiotics.
For more information, please see:
An awesome video of the working ribosome: http://www.youtube.com/watch?v=Jml8CFBWcDs
Information about the ribosome: http://www.pdb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb10_1.html
A description of X-ray crystallography: http://publications.nigms.nih.gov/structlife/chapter2.html