Classic Experiment: Anfinsen's Experiment

The focus of this post is not to talk about much new science. Instead, it is to commemorate one of the classic experiments of biology, namely, Anfinsen's experiment. Anfinsen's experiment was an experiment that allowed scientists to conclude that the 3 dimensional structure of a protein was controlled by primary structure of the protein.

Most proteins have a elaborate 3-dimensional structure for it to properly work.  An example would be the structure of DNA ligase, a protein that can join 2 bits of DNA together. 

If DNA ligase did not have this structure, it probably would not function properly. But how does DNA ligase know to assume this structure? What Anfinsen showed was that the DNA ligase itself knew that it had to assume this structure. 

How did it know it had to assume this structure? It just does. In the future, we may examine protein folding mechanics, but for now, let's just leave it here. 

How did Anfinsen showed that the final form of the protein could be obtained without help from other components in the cell. He took a protein called ribonuclease and unfolded it (using chemicals called urea and beta-mercaptoethanol)

Then Anfinsen removed the urea and beta-mercaptoethanol. He then left unfolded ribonuclease alone and the next day, ribonuclease refolded again, in solution without the help of other cellular components (such as other proteins).

This showed that the primary structure of the protein, just the sequence of amino acids, has enough information to determine the final three-dimensional structure. This was a very significant discovery that led Anfinsen to receive the 1972 Nobel Prize in Chemistry, along with Stanford Moore and William H. Stein. 

For further information, check out the link to the Nobel Prize in Chemistry. Also, if you are interested, check out these two books. The first book, Biology: Concepts and Connections, is a very well written general biology book that is has a nice introduction to protein biology. The second book is a more advanced book on protein biology.