Progress In Protein Crystallography

By Author: Sergey Ruzheinikov
Total Articles: 3764
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Protein crystallography plays one of the most important roles in the structural study of the different proteins. Currently in is impossible to analyze protein functionality without knowing the exact molecular structure of this particular protein. The detailed information about positions of all amino acid residues is crucially important for analysis of protein function.

The protein crystallography is relatively young branch of science, which was started from studies of the DNA-double helix structure by James Watson and Francis Crick in April 1953. Currently, it is possible to solve the structure of whole virus with atomic resolution by this technique.

From this time the bimolecular crystallography made great breakthrough. It was possible only due to the development of computing power of modern computers. The computational requirements of protein crystallography are enormous. For example, the structure of leucine dehydrogenase contains eight polypeptide chains, each of them contains 350 amino acids, and each of them contains about 15 atoms. So, finally we've got about 40 thousand atoms. For each atom we can calculate ...
... three positional and between one and nine temperature factors. Then for the simple case we need define about 160 thousand parameters, or about half-million for difficult, high resolution case. Minimization of equation with such amount of independent parameters is not very simple task. Data collection is complicated as well. Modern detectors generate about 30 Mb of raw data per few second. The storage of such informational flow is another problem for computer techniques. Luckily, last few years these computational problems were solved.

Modern protein structures, solved by protein crystallography allow to identify not only the exact position of each atoms, including the position of hydrogen atoms but also detect the structural changes related with the enzymatic reactions. This will allow to investigate in great details many of the enzymatic reactions, which was previously only predicted on the basis of the catalytic amino acid residues and on the basis of the static picture of these amino acid residues. These data will be very useful in medicine, biotechnology and other field of human life. The most important is the drug design which is impossible without the knowledge of enzymatic act.

Despite the great progress in protein structural studies, there are lot of protein problems which not solved yet. For example, despite the exact knowledge about structures of more than ten thousand protein structures, we do not understand the principles of protein organization and it is almost impossible to predict protein structure. The other problem is to understand the evolution of proteins. Currently we know the static picture of protein structures, but how they appear from scratch? At the moment only small ideas and examples of protein evolution are known. Another great white area in our knowledge is the protein crystallization. We can produce almost any protein by genetic techniques. After this protein purification is a quite routine procedure with the set of standard routines and procedures, but the final step, the protein crystallization is a matter of luck, rather than science. The only one thing can get the results - many trials of different crystallization conditions and maybe lucky you to grow 0.1mm protein crystal.

As a conclusion it is possible to note, that despite that protein crystallography is more than 50 year old, this scientific area still have many unsolved problems and it is very interesting and perspective area of science for young biologist, chemist and physicist.